Search

Selective photothermolysis has limitations in efficacy and safety for dermal targets. We describe a novel concept using scanned focused laser microbeams for precise control of dermal depth and pattern of injury, using a 1550 nm laser that generates an array of conical thermal zones while minimizing injury to the epidermis. To characterize the conical thermal zones in vivo and determine safe starting parameters to transition to a second phase to explore potential clinical indications. A focused toroidal (ring) laser beam was delivered through a cold sapphire window, sparing epidermal injury in a central zone. Pulse energy, lesion depth, density, and energy delivery were titrated in ex vivo human skin and subsequently on the backs of 21 human subjects. Histology showed microscale patterns of thermal injury, which varied predictably with laser parameters. Time-course healing through histology and skin surface imaging demonstrated the ability of the device to deliver high energies without sequelae. Clinical data are currently being collected to further explore the safety and efficacy of the device. The 1550 nm laser with focal point technology enables precise control of lesion depth while simultaneously sparing a large portion of the epidermis, lowering the risk of adverse effects. [ABSTRACT FROM AUTHOR]

A detailed experimental analysis of the impact of device topology on the performance of 1550 nm VCSELs with an active region based on thin InGaAs/InAlGaAs quantum wells and a composite InAlGaAs buried tunnel junction is presented. The high-speed performance of the lasers with L-type device topology (with the largest double-mesa sizes) is mainly limited by electrical parasitics showing noticeable damping of the relaxation oscillations. For the S-type device topology (with the smallest double-mesa sizes), the decrease in the parasitic capacitance of the reverse-biased p+n-junction region outside the buried tunnel junction region allowed to raise the parasitic cutoff frequency up to 13–14 GHz. The key mechanism limiting the high-speed performance of such devices is thus the damping of the relaxation oscillations. VCSELs with S-type device topology demonstrate more than 13 GHz modulation bandwidth and up to 37 Gbps nonreturn-to-zero data transmission under back-to-back conditions at 20 °C. [ABSTRACT FROM AUTHOR]

Single-mode long-wavelength (LW) vertical-cavity surface-emitting lasers (VCSELs) present an inexpensive alternative to DFB-lasers for data communication in next-generation giga data centers, where optical links with large transmission distances are required. Narrow wavelength-division multiplexing systems demand large bit rates and single longitudinal and transverse modes. Spatial division multiplexing transmission through multicore fibers using LW VCSELs is enabling still larger-scale data center networks. This review discusses the requirements for achieving high-speed modulation, as well as the state-of-the-art. The hybrid short-cavity concept allows for the realization of f3dB frequencies of 17 GHz and 22 GHz for 1300 nm and 1550 nm range VCSELs, respectively. Wafer-fusion (WF) concepts allow the realization of long-time reliable LW VCSELs with a record single-mode output power of more than 6 mW, 13 GHz 3 dB cut-off frequency, and data rates of 37 Gbit/s for non-return-to-zero (NRZ) modulation at 1550 nm. [ABSTRACT FROM AUTHOR]

The GaAs-based material system is well-known for hosting InAs quantum dots (QDs) with outstanding optical properties, typically emitting at a wavelength of around 900 nm. The insertion of a metamorphic buffer (MMB) can shift this emission to the technologically attractive telecom C-band range centered at 1550 nm. However, the thickness of common MMB designs (>1 μm) limits their compatibility with most photonic resonator types. Here, we report on the metal–organic vapor-phase epitaxy (MOVPE) growth of a novel InGaAs MMB with a nonlinear indium content grading profile designed to maximize plastic relaxation within minimal layer thickness. This allows us to achieve the necessary transition of the lattice constant and to provide a smooth surface for QD growth within 180 nm. Single-photon emission at 1550 nm from InAs QDs deposited on top of this thin-film MMB is demonstrated. The strength of the new design is proven by integrating it into a bullseye cavity via nano-structuring techniques. The presented advances in the epitaxial growth of QD/MMB structures form the basis for the fabrication of high-quality telecom nonclassical light sources as a key component of photonic quantum technologies.

A detailed experimental analysis of the impact of device topology on the performance of 1550 nm VCSELs with an active region based on thin InGaAs/InAlGaAs quantum wells and a composite InAlGaAs buried tunnel junction is presented. The high-speed performance of the lasers with L-type device topology (with the largest double-mesa sizes) is mainly limited by electrical parasitics showing noticeable damping of the relaxation oscillations. For the S-type device topology (with the smallest double-mesa sizes), the decrease in the parasitic capacitance of the reverse-biased p+n-junction region outside the buried tunnel junction region allowed to raise the parasitic cutoff frequency up to 13–14 GHz. The key mechanism limiting the high-speed performance of such devices is thus the damping of the relaxation oscillations. VCSELs with S-type device topology demonstrate more than 13 GHz modulation bandwidth and up to 37 Gbps nonreturn-to-zero data transmission under back-to-back conditions at 20 °C.

Lasers used for space communication, lidar, and laser detection in space-air-ground integration applications typically use a traditional 1550 nm band tunable distributed-feedback Bragg (DFB) semiconductor laser. This has low output power, complex fabrication process, and high fabrication cost. In this paper, we present a gain-coupled surface grating-based 1550 nm DFB semiconductor laser that can be fabricated without the use of secondary epitaxial growth techniques or high-precision lithography. The periodic electrical injection is used to achieve a gain coupling effect. A tapered waveguide is added to achieve a high output power, and the use of AlGaInAs multiple quantum wells in the active region reduces the linewidth of the laser. A continuous-wave (CW)output power of 401.5 mW is achieved at 20 °C, the maximum side mode rejection ratio exceeds 55 dB, the measured 3 dB linewidth is 18.86 MHz, and the stable single-mode output with a quasi-continuous tuning range of 6.156 nm near 1550 nm from 10 °C to 50 °C. This simple preparation method, low cost, excellent performance, and stable tunable laser have extremely high commercial value in applications such as space communication, lidar, and laser detection. [ABSTRACT FROM AUTHOR]

The continuous improvement of current gravitational wave detectors (GWDs) and the preparations for next generation GWDs place high demands on their stabilized laser sources. Some of the laser sources need to operate at laser wavelengths between 1.5 μ m and 2.2 μ m to support future detectors based on cooled silicon test masses for thermal noise reduction. We present detailed characterizations of different commercial low power seed laser sources and power amplifiers at the wavelength of 1550 nm with respect to performance parameters needed in GWDs. A combination with the most complete set of actuators was arranged as a master-oscillator power amplifier (MOPA), integrated into a stabilization environment and characterized. We present the results of this characterization that make this stabilized MOPA a highly relevant prototype for future GWDs as well as a low noise light source for other experiments in high precision metrology. [ABSTRACT FROM AUTHOR]

Background: Selective photothermolysis has limitations in efficacy and safety for dermal targets. We describe a novel concept using scanned focused laser microbeams for precise control of dermal depth and pattern of injury, using a 1550 nm laser that generates an array of conical thermal zones while minimizing injury to the epidermis., Objective: To characterize the conical thermal zones in vivo and determine safe starting parameters to transition to a second phase to explore potential clinical indications., Methods: A focused toroidal (ring) laser beam was delivered through a cold sapphire window, sparing epidermal injury in a central zone. Pulse energy, lesion depth, density, and energy delivery were titrated in ex vivo human skin and subsequently on the backs of 21 human subjects., Results: Histology showed microscale patterns of thermal injury, which varied predictably with laser parameters. Time-course healing through histology and skin surface imaging demonstrated the ability of the device to deliver high energies without sequelae., Limitations: Clinical data are currently being collected to further explore the safety and efficacy of the device., Conclusion: The 1550 nm laser with focal point technology enables precise control of lesion depth while simultaneously sparing a large portion of the epidermis, lowering the risk of adverse effects., Competing Interests: Conflicts of interest Drs Manstein, Chan, Anderson, and Erenburg are all founders of Blossom Innovations. Author Escobar is an employee of Blossom Innovations. Drs Bhawalkar and Erenburg and Author Katkam are employees of AVAVA Inc. Drs Pomerantz, Tannous, Yoo and Tran were consultants to AVAVA Inc. AVAVA Inc. is a Blossom Innovations company., (Copyright © 2024 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.)

Lasers used for space communication, lidar, and laser detection in space-air-ground integration applications typically use a traditional 1550 nm band tunable distributed-feedback Bragg (DFB) semiconductor laser. This has low output power, complex fabrication process, and high fabrication cost. In this paper, we present a gain-coupled surface grating-based 1550 nm DFB semiconductor laser that can be fabricated without the use of secondary epitaxial growth techniques or high-precision lithography. The periodic electrical injection is used to achieve a gain coupling effect. A tapered waveguide is added to achieve a high output power, and the use of AlGaInAs multiple quantum wells in the active region reduces the linewidth of the laser. A continuous-wave (CW)output power of 401.5 mW is achieved at 20 °C, the maximum side mode rejection ratio exceeds 55 dB, the measured 3 dB linewidth is 18.86 MHz, and the stable single-mode output with a quasi-continuous tuning range of 6.156 nm near 1550 nm from 10 °C to 50 °C. This simple preparation method, low cost, excellent performance, and stable tunable laser have extremely high commercial value in applications such as space communication, lidar, and laser detection.

The continuous improvement of current gravitational wave detectors (GWDs) and the preparations for next generation GWDs place high demands on their stabilized laser sources. Some of the laser sources need to operate at laser wavelengths between 1.5 μm and 2.2 μm to support future detectors based on cooled silicon test masses for thermal noise reduction. We present detailed characterizations of different commercial low power seed laser sources and power amplifiers at the wavelength of 1550 nm with respect to performance parameters needed in GWDs. A combination with the most complete set of actuators was arranged as a master-oscillator power amplifier (MOPA), integrated into a stabilization environment and characterized. We present the results of this characterization that make this stabilized MOPA a highly relevant prototype for future GWDs as well as a low noise light source for other experiments in high precision metrology.

We report that an ErAs quantum-dot array in a GaAs matrix under 1550 nm pulsed excitation produces cooperative spontaneous emission—Dicke superradiance—in the terahertz frequency region at room temperature. Two key points pertain to the experimental evidence: (i) the pulsed THz emission power is much greater than the continuous wave (CW) photomixing power; and (ii) the ultrafast time-domain waveform displays ringing cycles. A record of ~117 μW pulsed THz power was obtained, with a 1550 nm-to-THz power conversion efficiency of ~0.2%. [ABSTRACT FROM AUTHOR]

Abstract: In this letter we propose, for the very first time, a Molybdenum based Yagi‐Uda high‐directional nantenna. It is realized using simple Low Pressure Chemical Vapor Deposition (LPCVD) technique on a silicon substrate for 1550 nm standard optical communication system. The proposed nantenna uses Molybdenum metal as a ground plane while the Yagi‐Uda driven, radiator and directing elements are made up of Aluminum. Grounded Co‐Planar Waveguide (GCPW) technique is used for exciting the nanoantenna in CST Microwave Studio simulator. The nantenna achieves an impedance bandwidth of (193.37–193.71 THz) at a center frequency of 193.5 THz with a high gain and directivity of 12.9 and 16.6 dB, respectively. Near‐field and far‐field performance of the proposed nantenna is also demonstrated via extensive numerical simulations. The results achieved makes the proposed nantenna a viable candidate for applications in the field of nanophotonic circuits and photovoltaic devices working in the optical C‐band window. [ABSTRACT FROM AUTHOR]

• The ternary sulfide of NaYS 2 was adopted as a novel host for high-efficient UCL. • Er3+ single-doped NaYS 2 was designed to avoid luminescence quenching via CTS. • Breakthrough upconversion brightness and efficiency were achieved in the NaYS 2 :Er3+. • The mechanisms for high-efficiency UCL and color stability were studied. Optimizing the host lattice is the most efficient strategy to break through the intrinsic characteristic of low efficiency up-conversion luminescence (UCL). In principle, ternary sulfide, e.g. NaYS 2 , is an ideal UCL host matrix due to its low phonon energy and highly asymmetrical crystal structure. However, it was found that the low lying S2-→Yb3+ charge transfer state (CTS) existing in the ternary sulfide material severely quenches the UCL under 980 nm excitation, which generally employs Yb3+ ion as the conventional sensitizer. Herein, we design Er3+ single-doped NaYS 2 phosphors for highly efficient UCL under 1550 nm excitation. This novel NaYS 2 :Er3+ phosphor excited at 1550 nm exhibits a 94-fold enhancement of UCL intensities compared to that of conventional NaYS 2 :Yb3+,Er3+ under 980 nm excitation. More encouragingly, compared to the commercial β-NaYF 4 :Yb3+,Er3+ phosphors, the UCL efficiency and brightness of NaYS 2 :Er3+ excited at 1550 nm are twice that of β-NaYF 4 :Yb3+,Er3+ excited at 980 nm. Such extraordinary efficient UCL is accomplished by taking advantages of the intrinsic low phonon energy (279 cm−1) of the NaYS 2 host and the highly asymmetrical trigonal crystal system. Furthermore, in the Er3+ single-doped NaYS 2 system, the S2-→Er3+ CTS lies at a high state of ≈34500 cm−1, which will not quench the efficient UCL from Er3+ ions. The large absorption cross-section at 4I 13/2 energy level (high response to 1550 nm radiation) and long lifetime of the metastable state of 4I 9/2 also contribute to the population of the emission levels (2H 11/2 /4S 3/2). These findings provide a new class of host materials for achieving highly efficient UCL. [ABSTRACT FROM AUTHOR]

We report that an ErAs quantum-dot array in a GaAs matrix under 1550 nm pulsed excitation produces cooperative spontaneous emission—Dicke superradiance—in the terahertz frequency region at room temperature. Two key points pertain to the experimental evidence: (i) the pulsed THz emission power is much greater than the continuous wave (CW) photomixing power; and (ii) the ultrafast time-domain waveform displays ringing cycles. A record of ~117 μW pulsed THz power was obtained, with a 1550 nm-to-THz power conversion efficiency of ~0.2%.

Efficiently up-conversion luminescence can be achieved by replacing the traditional sensitizer Yb 3+ ions with Er 3+ ions in LaVO 4 host under 1550 nm excitation. In contrast to other up-conversion luminescence materials, such as Y 2 O 2 S:Er 3+ , Y 2 O 3 :Er 3+ , YOCl:Er 3+ , which exhibit red emission, LaVO 4 :Er 3+ samples present an abnormal green emission under 1550 nm excitation. Excited state absorption is the dominating up-conversion luminescence mechanism at low doping concentrations of Er 3+ , whereas energy transfer up-conversion predominates at high concentrations of Er 3+ . Infrared thermal imaging is adopted to investigate the thermal effects of LaVO 4 :Er 3+ sample under 1550 nm irradiation. It shows a rapid heating process within 1 ∼ 5 s and LaVO 4 :0.21Er 3+ sample yields a temperature rising of ΔT = 66.46 °C under 1550 nm irradiation (207 mW) within 60 s. Therefore, the temperature sensor based on up-conversion luminescence of Er 3+ ions 2 H 11/2 / 4 S 3/2 thermally coupled levels produced significant measurement errors at low temperatures because of the thermal effects and non-uniform temperature of the incident light spot area. [ABSTRACT FROM AUTHOR]

Red emission with high color purity in Y 2 Ti 2 O 7 :Yb 3+ ,Er 3+ material is successfully obtained by high-concentration doping of Yb 3+ and Er 3+ under 980 and 1550 nm excitation based on the special layer structure of pyrochlore crystal. It shows that Yb 3+ ion content and excitation wavelength greatly influence the red emission percent of total up-conversion luminescence intensity of Y 2 Ti 2 O 7 :Yb 3+ ,Er 3+ . Y 2 Ti 2 O 7 :Yb 3+ ,Er 3+ shows much better red color purity at 1550 nm excitation than at 980 nm. Furthermore, the co-doping of Yb 3+ ions considerably boosts the red emission under 980 or 1550 nm pumping with different luminescence mechanisms compared with Y 2 Ti 2 O 7 :Er 3+ sample. The red emission percent of total up-conversion luminescence intensity gradually increases with the increment of Yb 3+ concentration at both excitation sources. The red-to-green emission ratio of the sample is 6.97 (980 nm) and 23.26 (1550 nm) when the Yb 3+ content is 30 mol%. [ABSTRACT FROM AUTHOR]

• Multi-component fluoride nanocrystal Pb x Na y-n Li n Y z F 2x+y+3z+3m : Er3+ m with a response in the 1.5 μm band was synthesized by the low temperature combustion synthesis method. • When the concentration of Li+ ion is 2.07 mol%, the up-conversion luminescence intensity is obviously improved. • The hypothetical physical mechanism model for the luminescence intensity of Li+ ion enhanced materials was confirmed. • Innovatively established a dual-fuel system, and systematically analyzed the heat release characteristics of each fuel system, and prepared nanocrystals with high luminous intensity and fine particles. A 1.5 μm multi-component fluoride nanocrystal Pb x Na y-n Li n Y z F 2x+y+3z+3m : Er3+ m was synthesized by the low temperature combustion synthesis (LCS) method. On the basis of the orthogonal experiment and optimization experiment, Li+ ion was introduced into the matrix and the dual-fuel system was established, and the up-conversion luminescence intensity was enhanced by changing the matrix composition and improving the process methods. The results show that when the concentration of Li+ ion is 2.07 mol%, the fuel consumption in the dual-fuel system is 2.2 stoi., 0.7 stoi., the up-conversion luminescence intensity is obviously improved. The structure and morphology of samples were analyzed by the X-ray diffraction (XRD) and scanning electron microscopy (SEM), and a schematic model of physical mechanism for the luminescence intensity of Li+ ion enhanced materials was confirmed. The exothermic characteristics of the dual-fuel system were analyzed by the differential scanning calorimetry and thermogravimetric analysis (DSC-TGA). The influence of the introduction of Li+ ion and the dual-fuel system on the luminescence intensity was discussed in detail. [ABSTRACT FROM AUTHOR]

Objective:To evaluate the efficacy and side effects of 1550-nm fractional Er:Glass laser in treating atrophic acne scar.Materials and methods:Thirty Chinese patients aged 18–65 with atrophic acne scars on both cheeks received a split-face treatment, one side with four sessions of treatment with fractional 1550-nm Er:Glass laser at 20-day interval and the other with topical asiaticoside cream application three times daily as control. Clinical response and side effects were evaluated by a dermatologist three weeks after each treatment and again 12 weeks after the last laser treatment. In addition, self-evaluation of satisfaction by the patients was done at the end of treatment.Results:The study found that mean scores decrease after treatment was 5.65 ± 4.34 for the treated side and 1.23 ± 3.41 for the control side. The improvement in acne scars after the fractional Er:Glass laser 1550-nm treatment was more significant than the control side (p= 0.0001). The side effects were mainly local skin irritation and erythema, which disappeared within one week.Conclusion:The research results show that the fractional 1550-nm Er:Glass laser is an effective and safe treatment device for atrophic acne scars. [ABSTRACT FROM PUBLISHER]

We report the work on erbium:ytterbium-doped double clad fibre laser (EYDFL), that is pumped at 976 nm. The maximum output power generated is 13.6 W in 1550 nm region with a slope efficiency of about 21%. To the best of our knowledge, this is the highest power reported from an EYDFL, that uses commercially available off-the-shelf large mode area Er:Yb-doped double-clad fibre. [ABSTRACT FROM AUTHOR]

This paper introduces a wavelength multiplexer (MUX) using the extraneous self-imaging (Ex_SI) phenomenon, which is not mentioned in multimode-interference theory. The Ex_SI phenomenon in silica-based multimode waveguides was experimentally studied. Then, using data for the Ex_SI phenomenon, the wavelength MUX for the wavelengths of 1310 and 1550 nm was developed. The optimum length of the multimode waveguide, with a width of 18 mum, was confirmed as a 3670- mum wavelength MUX. For the wavelengths of 1310 and 1550 nm, the excess losses were determined to be -0.4 and -0.45 dB, respectively, while the extinction ratios were 16.9 and 19.7 dB, respectively [ABSTRACT FROM PUBLISHER]

Based on a comprehensive theoretical model of a recently proposed novel technique known as adaptively modulated optical orthogonal frequency-division multiplexing (AMOOFDM), investigations are undertaken into the impact of an analog-to-digital converter involved in the AMOOFDM modem on the transmission performance of AMOOFDM signals in unamplified intensity-modulation and direct-detection (IMDD) multimode-fiber (MMF)-based links. It is found that signal quantization and clipping effects are significant in determining the maximum achievable transmission performance of the AMOOFDM modem. A minimum quantization bit value of ten and optimum clipping ratio of 13 dB are identified, based on which, the transmission performance is maximized. It is shown that 40-Gb/s-over-220-m and 32-Gb/s-over-300-m IMDD-AMOOFDM signal transmission at 1550 nm with loss margins of about 15 dB is feasible in the installed worst case 62.5-mum MMF links having 3-dB effective bandwidths as small as 150 MHz middot km. Meanwhile, excellent performance, robustness to fiber types, and variation in launch conditions and signal bit rates is observed. In addition, discussions are presented of the potential of 100-Gb/s AMOOFDM signal transmission over installed MMF links [ABSTRACT FROM PUBLISHER]

Optical thermometers have been widely investigated. Here, the temperature behavior of second harmonic generation (SHG) in periodically poled lithium niobate (PPLN) substrates is analyzed; indeed, the QPM tuning in PPLN devices and the obtained SHG efficiency depend on the crystal thermal expansion and dispersion, particularly in the case of guided propagation. Therefore, such devices are suitable to realize optical thermometers for demanding applications. This investigation originated with the request of a thermometer to be installed on the pantographs of high-speed trains. Therefore, it must be sturdy and reliable, but it has even to work in an EMD environment. The temperature behavior of the SHG was theoretically modeled and experimentally validated at 1550 nm, in both bulk propagation and APE channel waveguides. In the first case, by using a 10-mW source, which was obtained from a laser diode and a fiber amplifier, an accuracy of 0.3 degC was found. The pump power was about three orders of magnitude smaller in guided propagation. In view of testing on the trains, our investigation resulted in the design of a device without mechanical contacts with the input and output fibers. Since it works in free propagation, there are no serious alignment and packaging problems. The performances, which are expected to be the same of our tests, widely satisfy all the requirements for working effectively in a strongly hostile and EMD environment and for giving accurate measurements on a wide range of temperatures [ABSTRACT FROM PUBLISHER]

We have fabricated low-stress polyimide membranes for use as high-resolution variable optical attenuator (VOA). Polyimide membranes are assembled with fiber collimators to perform 3-D beam spoiling that varies the optical power with 0.01-dB resolution. The measured residual stress and Young's modulus of the polyimide membrane are 3.2 MPa and 15 GPa, respectively. The 41-mum deformation of the membrane is demonstrated by the electrostatic force with 170 volts. The 0.46-dB insertion loss and >15-dB dynamic range are achieved at 1550-nm wavelength [ABSTRACT FROM PUBLISHER]

Multifiber interconnection technology is one of the important keys to increase package density in optical networks. We present a novel releasable multifiber optical connectivity solution from the initial concept to the functional prototypes. This connectivity solution relies on a V-groove alignment platform and a microlens array. It can, e.g., provide reliable connections between a fiber array and an active optoelectronic component array or between a fiber array and an optical waveguide device. Moreover, within a free-space propagation region, it provides access to collimated optical beams, thus enabling various light manipulation options. The microlens V-groove fabrication process makes use of a dedicated assembly station that has been designed for automation. The microlens array is positioned on the platform, aligned relative to the V-grooves, and fixed with a low-cost adhesive bonding technology. Uniform and stable low losses for fiber-to-fiber coupling via two lenses have been achieved for single-mode and multimode fibers at wavelengths of 850, 1300, and 1550 nm. This connectivity solution represents, therefore, a versatile cost-effective technology for releasable connections of fiber arrays to any other optical multiport device [ABSTRACT FROM PUBLISHER]

We report triple wavelength demultiplexers adopting a thin-film filter (TFF) and a waveguide Bragg grating as a reflector for low-cost integrated optical triplexer transceivers deployed for the triple play service-based fiber-to-the-home (FTTH) networks. In the proposed demultiplexers, 1310- and 1550-nm lights were designed to be divided after passing the planar lightwave circuit-based directional coupler by half-cycle and full-cycle coupling actions, respectively. The 1490-nm light was reflected by a TFF or Bragg grating. The losses of the demultiplexers were less than 2.0 dB at all ports. The average crosstalk among the three lights for the demultiplexers was about -20 dB or better. Through a single reflector, the demultiplexer structures are significantly simplified, and cost is reduced. The proposed triple wavelength demultiplexers provide cost-effective and high-performance solutions for FTTH network systems [ABSTRACT FROM PUBLISHER]

Single-mode (SM) ultrashort optical interconnections between the fibers and waveguides using self-forming polymeric waveguides with low optical losses at 1300 and 1550 nm were demonstrated. The localized refractive index in the SM regime is estimated by measuring the surface topography induced by monomer diffusion during the waveguide formation. A loss less than -1 dB can be obtained from self-aligning SM-to-multimode (MM) fibers and SM-to-SM fibers interconnections, respectively. A self-formed waveguide-to-fiber interconnection is fabricated and measured with loss less than 0.2 dB at 1550 nm. The polymer waveguide relaxes the positioning requirements for single-mode chip-to-chip optical interconnections, showing great potential to improve the short-term yield and long-term reliability [ABSTRACT FROM PUBLISHER]

The monolithic integration of components holds promise to increase network functionality and reduce packaging expense. Integration also drives down yield due to manufacturing complexity and the compounding of failures across devices. Consensus is lacking on the economically preferred extent of integration. Previous studies on the cost feasibility of integration have used high-level estimation methods. This study instead focuses on accurate-to-industry detail, basing a process-based cost model of device manufacture on data collected from 20 firms across the optoelectronics supply chain. The model presented allows for the definition of process organization, including testing, as well as processing conditions, operational characteristics, and level of automation at each step. This study focuses on the cost implications of integration of a 1550-nm DFB laser with an electroabsorptive modulator on an InP platform. Results show the monolithically integrated design to be more cost competitive over discrete component options regardless of production scale. Dominant cost drivers are packaging, testing, and assembly. Leveraging the technical detail underlying model projections, component alignment, bonding, and metal-organic chemical vapor deposition (MOCVD) are identified as processes where technical improvements are most critical to lowering costs. Such results should encourage exploration of the cost advantages of further integration and focus cost-driven technology development [ABSTRACT FROM PUBLISHER]

To the best of our knowledge, for the first time, a single-crystal silicon carbide (SiC)-based minimally invasive smart optical sensor suited for harsh environments has been designed and demonstrated. The novel sensor design is based on an agile wavelength source, instantaneous single-wavelength strong two-beam interferometry, full optical power cycle data acquisition, free-space targeted laser beams, multiple single-crystal-thick SiC optical front-end chips, and multiwavelength signal processing for unambiguous temperature measurements to form a fast and distributed smart optical sensor system. Experiments conducted using a 1550-nm eye-safe band-tunable laser and a 300-mum coating-free thick SiC chip demonstrate temperature sensing from room temperature to 1000degC with an estimated average 1.3degC resolution. Applications for the proposed sensor include use in fossil fuel-based power systems, aerospace/aircraft systems, satellite systems, deep-space exploration systems, and drilling and oil mining industries [ABSTRACT FROM PUBLISHER]

A new concept for a 1 times 2 micromechanical optical switch with 10 mus of switching speed, 29 dB of ON/OFF ratio, and insertion loss of -7.22 dB for lambda=1550 nm and -4.96 dB for lambda=635 nm is presented. The idea is to insert a micromechanical switching mechanism composed of a vertical silicon cantilever beam inside a hollow planar optical waveguide structured in a silicon-on-insulator (SOI) wafer. The switching beam in the Y hollow waveguide is electrostatically actuated, which makes it deflect to one side or the other in order to redirect light in one of the two outputs. Switching times of less than 10 mus were measured with the produced devices. Compared to classical microelectromechanical systems (MEMS) switches, the concept presents the advantage to decrease the risks of misalignment between the mirror and the optical waveguide, as the two elements are defined in the same process step, and as the mirror position is less critical than for classical MEMS switches. It also limits the optical losses due to beam spreading that occurs in free-space configuration. Three different optical surfaces for the hollow waveguides were studied-a gold coating, an antiresonant reflecting optical waveguide (ARROW) optical coating, and bare hollow silicon [ABSTRACT FROM PUBLISHER]

In this paper, a model is presented for the simulation of integrated passively mode-locked InP-InGaAsP ring laser systems that include active components such as an amplifier and saturable absorber, and passive components that can be frequency dispersive. These dispersive components can have a complex frequency dependence, such as arrayed waveguide gratings (AWGs). The model is a lumped-element model that is used as a design tool for developing integrated femtosecond pulse sources with internal dispersion control. Simulations based on an InP/InGaAsP amplifier and absorber show the possibility of laser designs that are able to generate pulses with pulse durations down to 300 fs in the 1550-nm wavelength range. The designs are based on femtosecond laser systems in bulk and fiber optics that are published in the literature. The femtosecond laser sources presented here can be realized using existing InP-InGaAsP active-passive integration technology. [ABSTRACT FROM PUBLISHER]

On quantum communication technologies based on an optical fiber channel, for example a quantum key distribution, it is essential to generate a single photon and a correlated photon pair at telecom wavelength efficiently. We report on the single-photon generation at 1550 nm using photon pairs generated by the spontaneous parametric down-conversion. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 89(2): 8–18, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20227 [ABSTRACT FROM AUTHOR]

A single-mode waveguide and a 1 × 3 multimode interference (MMI) power splitter are fabricated in hybrid zirconium (Zr)-doped sol-gel material by a microreplication technology with a polydimethylsiloxane (PDMS) replica. The power splitter, as optimized using a finite-difference beam-propagation method (FD-BPM) simulation with self-imaging effects, represents one of the first experimental demonstrations of a high-tolerance manufactured device using replication methods. The fabrication of the microreplicated power splitter demonstrates high-quality optical and geometrical properties. The local uniformity in thickness of the multimode waveguide is less than 1.0%, and the average surface roughness is about 5.35 nm. The measured splitting loss is less than 0.6 dB for both transverse polarizations at the 1550-nm wavelength. Experimental achievements indicate that the soft lithography technology allows for the performance of applications in integrated optical devices in Zr-doped sol-gel materials with high standards. [ABSTRACT FROM PUBLISHER]

In this paper, the tuning mechanism for a two-dimensional (2-D) guided-wave photonic-crystal (PhC) filter obtained by varying the angle-of-incidence in the waveguide plane is demonstrated. Modeling and design of the filter have been carried out by using the Bloch-Floquet formalism. The device shows a resonance wavelength at 1550 nm for the p=30 order at normal incidence. The free spectral range (FSR) is about 38 nm and can be spanned with an in-plane angle of incidence θ ranging from 0° to 14°. The full width at half maximum (FWHM) is in the range 0.14-0.18 nm. The filter performance is suitable for 50-GHz dense-wavelength-division-multiplexing (DWDM) systems and shows that variable oblique incidence can be exploited as a tuning mechanism. [ABSTRACT FROM PUBLISHER]

A novel optical signal modulation concept of adaptively modulated optical orthogonal frequency division multiplexing (AMOOFDM) is proposed, and a comprehensive theoretical model of AMOOFDM modems is developed. Numerical simulations of the transmission performance of the AMOOFDM signals are undertaken in unamplified multimode fiber (MMF)-based links using directly modulated distributed feedback (DFB) lasers (DMLs). It is shown that 28 Gb/s over 300 m and 10 Gb/s over 900 m transmission of intensity modulation and direct detection (IMDD) AMOOFDM signals at 1550 nm is feasible in DML-based links using MMFs with 3-dB effective bandwidths of 200 MHz·km. Apart from a higher signal capacity, AMOOFDM also has a greater spectral efficiency and is less susceptible to different launching conditions, modal dispersion, and fiber types, compared with all existing schemes. In addition, a large noise margin of about 15 dB is also observed. The bits of resolution of analog-to-digital converters (ADCs) and the cyclic prefix of AMOOFDM symbols are the main factors limiting the maximum achievable performance, on which the influence of DMLs is, however, negligible under the optimum operating condition. [ABSTRACT FROM PUBLISHER]

Polarization mode dispersion (PMD) is a potential limiting factor in long-haul high-speed optical communications, especially in systems beyond 10 Gb/s. Although considerable effort has been devoted to compensation methods for PMD, most of the research is restricted to a small bandwidth, within the limits of the first- and second-order PMD approximations. For the first-order approximation to be valid, the distortions induced by PMD must remain less than a few tenths of the pulse duration or the bit period for return-to-zero (RZ) or non-return-to-zero (NRZ) systems, respectively. In this work, as far as the authors know, the application of ultrafast optical pulse-shaping techniques for experimental broadband all-order PMD compensation is demonstrated for the first time. PMD is treated as arbitrary variations of state of polarization (SOP) and phase versus wavelength, in an all-order sense. Two fiber-pigtailed pulse shapers are implemented in a serial manner to compensate the polarization and phase spectra independently. The first step corrects the wavelength-dependent polarization states to a fixed wavelength-independent state. This reduces the PMD compensation problem to a generalized chromatic dispersion compensation problem. Consequently, equalization of the spectral phase in the second step restores the clean broadband pulse signal. In the experiments, compensation of subpicosecond pulses (14 nm bandwidth around 1550 nm) that are anomalously spread to more than 2 ps due to PMD is demonstrated. These results are potentially relevant for future ultra-high-speed time-division-multiplexed (TDM) systems. Research challenges that must be addressed to bring this approach to practical application are also briefly enumerated, and the potential for scaling to a range compatible with wavelength-division-multiplexed (WDM) systems is discussed. [ABSTRACT FROM PUBLISHER]

A long photonic-crystal fiber (PCF) with a low loss was successfully fabricated by first preparing a large pure silica glass preform. The fiber is 100 km long and has a low loss of 0.3 dB/km at 1550 nm. The fiber has a Rayleigh scattering coefficient of 0.85 dB/(km·μm4), which is the lowest value ever reported in a PCF. Using this fiber, the first penalty-free dispersion-managed soliton transmission at 10 Gb/s was achieved in a PCF. [ABSTRACT FROM PUBLISHER]

Optical rib waveguides with various widths and heights were fabricated on silicon-on-insulator (SOI) substrates. Silicon etching was based on dry etching with inductively coupled plasma (ICP)-type reactive ion etcher. The etching process was developed to ensure low optical losses. Propagation loss of 0.13±0.02 dB/cm was measured for the fundamental mode at the wavelength of 1550 nm in a curved 114-cm-long waveguide. The reflection losses were suppressed by applying atomic layer deposition (ALD) in the growth of antireflection coatings (ARCs). [ABSTRACT FROM PUBLISHER]

In this paper, the first fiber-coupled no-moving-parts scanning heterodyne interferometer design using a single acoustooptic device (AOD) is reported. The design features a high-stability inline reflective architecture with free-space-scanned minimally invasive sensing via a multizone reflective sensor chip. The common path fiber interconnection allows robust remoting of the compact sensing front end. A proof-of-concept sensing experiment measuring voltage-dependent birefringence is successfully conducted using a voltage-controlled nematic liquid crystal (NLC) sensor chip. The system features a 4.69-dB optical loss, a 200-MHz output frequency, and a 1550-nm eye-safe operation wavelength. Applications for the system include any fiber-remoted sensing using the proposed free-space minimally invasive interrogating optical beams. [ABSTRACT FROM PUBLISHER]

There is a growing need for compact, efficient integrated waveguide optical amplifiers for use in optoelectronic communication. Zn2Si0.5Ge0.5O4 (ZSG) doped with Er (ZSG-Er) is a promising new host material due to the high concentration of Er that can be incorporated and the high optical activity of the incorporated Er. In this paper, the absorption and emission cross sections of Er in ZSG-Er (to the authors' knowledge, for the first time) are measured both through photoluminescence spectra and direct gain and absorption measurements. Peak absorption and emission cross sections are about 3×10-24 m2 from a Landenburg-Fuchtbauer analysis of the photoluminescence spectra, comparable to measurements on other oxide-based glass amplifiers. The population statistics of the excited Er level, along with the excited-state lifetime, are determined through a novel frequency-domain method in which the spontaneous emission power at 1550 nm is measured as a function of frequency under a modulated 980-nm input. The determined lifetime of 2 ms is comparable to the 2.3 ms measured using a conventional pump-probe technique. The novel analysis technique yields the population statistics of the excited Er atoms and the lifetime of the excited Er state under given pumping conditions independent of the unknown and variable coupling in and out of the waveguide. This method predicts zero net gain at 70 mW, about what is observed. Comparison of calculated gain and absorption based on Er density and measured cross sections with measured gains suggest that only about 20%-30% of the Er in the material is optically active. A 4.7-cm-long sample demonstrated a signal enhancement of ∼13dB. Cavity characteristics were measured using an analysis of coherent reflection under no pumping. The facet reflectivity was determined to be 0.27, and the scattering/absorption loss was 1.05/cm, for a total distributed loss of 1.65/cm in a 4-cm cavity. These losses, compared with an estimated achievable gain of 0.25/cm under full inversion, suggest that optically pumped lasing at this concentration is not possible. Measurements of both the cross sections and population statistics, compared with actual gain and absorption properties, give insight into the - contribution of the Er dopant under different conditions and can be used to model and improve rare-earth-based amplifiers. [ABSTRACT FROM PUBLISHER]

Undoped fluoride glass slides have been exposed to pulsed 193-nm ultraviolet (UV) irradiation. Their absorption changes have been measured to evaluate UV-induced index changes using Kramers-Kronig relation. A layer-peeling polishing technique was applied to characterize the local UV-induced index change of highly absorbing glass. Index changes up to 1.75×10-4 have been evaluated with this method in fluorozirco-aluminate glass. Fluoroaluminate and fluorozirconate glass showed only small index changes of about 2.0×10-6 and 2.6×10-6 at a wavelength of 1550 nm. [ABSTRACT FROM PUBLISHER]

Semicooled operation at 40°C of electroabsorptive modulator integrated laser (EML) for intermediate reach communication has been demonstrated. Reproducible operation at the elevated temperature was achieved through a device parameter optimized based on the temperature dependence of the dc characteristics of EML and a design of multi-quantum-well structure providing both relevant output power and high-frequency bandwidth at 40°C. Good eye pattern and near zero chirp with the average power over 0 dBm are obtained at 40°C, with an estimated lifetime over 20 years. [ABSTRACT FROM PUBLISHER]

High-performance vertically illuminated Schottky photodiodes with indium-tin-oxide (ITO) Schottky layers were designed, fabricated, and tested. Ternary and quarternary III-V material systems (AlGaN-GaN, AlGaAs-GaAs, InAlGaAs-InP, and InGaAsP-InP) were utilized for detection in the ultraviolet (UV) (λ<400 nm), near-IR (λ∼850 nm), and IR (λ∼1550 nm) spectrum. The material properties of thin ITO films were characterized. Using resonant-cavity-enhanced (RCE) detector structures, improved efficiency performance was achieved. Current-voltage, spectral responsivity, and high-speed measurements were carried out on the fabricated ITO-Schottky devices. The device performances obtained with different material systems are compared. [ABSTRACT FROM PUBLISHER]

The design and fabrication of an electrostatic MEMS variable optical attenuator (VOA) is described. The VOA is a reflection type with a folded micromirror actuated by a comb-drive actuator. The VOA is fabricated by a simple single-mask process. One photolithography and subsequent deep silicon reactive ion etching define all the microstructures of the VOA. The folded micromirror structure can reduce the overall size of the device by enabling the parallel alignment of an input fiber and an output fiber. Lensed fibers are used to maximize the coupling efficiency and the ease of assembly. The electrooptic characteristics and dynamic characteristics of fabricated VOA are measured. The initial insertion loss is 0.5 dB at 1550 nm and the maximum attenuation is 45 dB, respectively. The polarization dependent loss is measured to be 0.2 dB at 20-dB attenuation. The response time for maximum attenuation is less than 5 ms. [ABSTRACT FROM PUBLISHER]