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We demonstrate a diode-laser-pumped solid-state 1.06 μm laser using a novel YAG/Nd:YAG/YAG composite ceramics with a sandwich structure. We optimize the laser performance using different output couplers, pumping beam waists, and cavity lengths. A maximum CW output power of 11 W for the YAG/Nd:YAG/YAG-ceramic laser is obtained at an absorbed pump power of 25 W resulting in a slope efficiency of 49.4%. The excellent output performance shows that the novel YAG/Nd:YAG/YAGceramic material has a great potential in applications with diode-laser pumping. [ABSTRACT FROM AUTHOR]

We report on a diode-pumped Tm:Gd 3 Ga 5 O 12 (GGG) laser at 2004 nm operated in continuous-wave mode with two-mirror linear cavity configuration. The maximum output power reaches 0.58 W with laser threshold absorbed pump power of about 0.39 W and overall slope efficiency of about 18.4%, which is believed to be the highest output power for Tm:GGG laser up to now. The Tm:GGG laser shows obvious thermally induced saturation of the output power, which indicated that power and efficiency scaling could be furtherly realized by more efficient thermal removal of the laser crystal. [ABSTRACT FROM AUTHOR]

• Highly efficient CW and pulsed operation of Yb:YPO 4 microchip laser is demonstrated. • 3.81 W of CW output power is generated with a slope efficiency of 71%. • Pulsed output average power of 1.67 W is produced in passively Q-switched operation. We report on the performance of an Yb:YPO 4 microchip laser that could be efficiently operated in both continuous-wave (CW) and passive Q-switching mode, with a 2D WS 2 acting as the saturable absorber. With 6.30 W of pump power absorbed, a CW output power of 3.81 W was generated, leading to an optical conversion efficiency of 60.5%, while the slope efficiency amounting to 71%. In passively Q-switched operation, a pulsed output power of 1.67 W was produced at 660 kHz of repetition frequency, with a slope efficiency of 52%; the largest pulse energy, minimum pulse width, and highest peak power, which were achievable with different output mirrors, were respectively 2.52 μJ, 67 ns, and 31.7 W. The results demonstrated in this work represent a significant improvement in CW and passive Q-switching performance of Yb:YPO 4 microchip lasers. [ABSTRACT FROM AUTHOR]

The authors have developed a new heterogeneous‐integration method for fabricating semiconductor lasers with high modulation efficiency on Si substrates. The method employs the direct bonding of an InP‐based active layer to the SiO2 layer of a thermally oxidised Si substrate (SiO2 /Si substrate), followed by the epitaxial growth of InP to form a buried heterostructure (BH). By using the InP membrane, the authors realise epitaxial growth of an InP on the InP membrane directly bonded to Si without crystal quality degradation. Both a theoretical estimation and photoluminescence measurements revealed that the total laser thickness must be less than the critical thickness determined by the applied thermal strain. The authors confirmed that the crystal quality of the BH is comparable to that fabricated on an InP substrate when using a 250‐nm‐thick InP‐based membrane. A distributed feedback laser fabricated on a SiO2 /Si substrate exhibited continuous‐wave operation up to 100°C and was directly modulated by a 40 Gbit/s non‐return‐to‐zero signal with a bias current of 15 mA. These results indicate that epitaxial growth using a directly bonded InP‐based active layer on a SiO2 /Si substrate allows us to achieve lasers with high modulation efficiency and to use a large‐scale Si wafer as a fabrication platform, resulting in low‐cost fabrication. [ABSTRACT FROM AUTHOR]

We demonstrate compact optically pumped microsquare cavity laser on InP-based multiple-quantum-wells material platform. Continuous-wave operation is achieved for microsquare cavity with footprint as small as 4 × 4 μm2. Numerical mode analysis and experimental characterization of the microsquare laser are conducted, and the results are compared with the commonly used microdisk cavity laser fabricated on the same platform. The microsquare laser shows a lower lasing threshold and infers a higher differential efficiency than the microdisk counterpart. The microsquare cavity laser has also sufficiently high quality factor, and higher pumping injection efficiency due to the more evenly distributed field profile as compared to that of the microdisk. Experimental result also shows that the microsquare laser has better temperature stability than the microdisk. These results promise a potential alternative laser structure for on-chip light source applications. [ABSTRACT FROM PUBLISHER]

An Yb3+, Ho3+ codoped all-fiber laser oscillating at ~2.05 μm in continuous-wave, employing a novel pump version, 1.064 μm, is reported. Low threshold (~0.8 W) and moderate slope efficiency (~15.6%) of lasing are obtained in the simplest nonoptimized Fabry-Perot cavity, composed of a couple of spectrally adjusted fiber Bragg gratings. High brightness of ~2.05-μm output is an attractive laser's feature, stemming from spatially single-mode operation and narrow optical spectrum (~70 pm at a 3-dB level), in the whole pumps' range. The laser demonstrates high stability: during uninterrupted few-hours-perday operation its output power fluctuates within a 3% range. [ABSTRACT FROM PUBLISHER]

A key limitation, especially for the continuous-wave operation of terahertz quantum cascade lasers, is the large amount of heat dissipated in the active region. We demonstrate an all-electrical technique for monitoring the lattice temperature and characterizing the thermal properties of the active region, using the waveguide of the device as a temperature sensor. We report a measured temperature difference between the heat sink and top waveguide layer of up to 27 K during the continuous-wave operation of GaAs/Al0.15Ga0.85As-based devices, lasing at 2.4 THz. A thermal model of the devices is used to determine the thermal conductivity of the active region perpendicular to the semiconductor interfaces to be 7.3 W/(m·K). [ABSTRACT FROM PUBLISHER]

Compact semiconductor light sources with high performance continuous-wave (CW) and single mode operation are highly demanded for many applications in the terahertz (THz) frequency range. Distributed feedback (DFB) and photonic crystal (PhC) quantum cascade (QC) lasers are amongst the leading candidates in this field. Absorbing boundary condition is a commonly used method to control the optical performance of a laser in double-metal confinement. However, this approach increases the total loss in the device and results in a large threshold current density, limiting the CW maximum output power and operating temperature. In this letter, a robust surface emitting continuous-wave terahertz QC laser is realized in a two-dimensional PhC structure by a second order Bragg grating extractor that simultaneously provides the boundary condition necessary for mode selection. This results in a 3.12 THz single mode CW operation with a 3 mW output power and a maximum operation temperature (Tmax) of 100 K. Also, a highly collimated far-field pattern is demonstrated, which is an important step towards real world applications. [ABSTRACT FROM AUTHOR]

We describe a robust manufacturing process for single-mode photonic crystal (PhC) vertical-cavity surface-emitting lasers (VCSELs). Various PhC designs are investigated to determine endlessly single-mode designs, whereby the same PhC design yields single-mode operation for three different wavelengths (780, 850, and 980 nm). The fabrication of the PhC pattern is based on a self-aligned optical lithography process. The fabrication process results in VCSELs with a maximum output power greater than 1 mW under continuous-wave (CW) operation with side-mode suppression ratio greater than 35 dB. We also show microfluidic laser structures that are enabled by our fabrication process, which integrate fluid channels into VCSELs. Optical and electrical properties of these microfluidic VCSELs are investigated with and without fluids present under CW and pulsed operation. A shift of the lasing wavelength is found with fluid insertion. [ABSTRACT FROM PUBLISHER]

The principal ideas of the thin-disk laser design will be illustrated and the advantages for operating different laser materials will be explained. The results for continuous-wave (CW) and Q-switched operation as well as for amplification of short (nanosecond) and ultrashort (picosecond, femtosecond) pulses demonstrate the potential of the thin-disk laser design. The scaling laws for this laser design show that the power limit for CW operation is far beyond 40 kW for one single disk and the energy limit is higher than 3 J from one disk in pulsed operation. Also, the applicability of the thin-disk laser concept to optically pumped semiconductor structures will be discussed. When pumping directly into the quantum wells, the energy defect between the pump photon and the laser photon can be smaller than 5%, thus reducing the waste heat generated inside the semiconductor structure. First results demonstrate the potential of this new concept. Finally, a short overview of the industrial realization of the thin-disk laser technology will be given. [ABSTRACT FROM PUBLISHER]

We demonstrate wide bandwidth operation in a semiconductor optical amplifier (SOA)-based fiber laser with a wavelength spacing of 25 GHz. A broadband multiwavelength filter based on superimposed and chirped fiber Bragg gratings is used for wavelength selection. Three different cavity configurations are presented and compared: 1) a single-SOA standing-wave cavity; 2) a single-SOA ring cavity; and 3) a double-SOA ring cavity. Up to 41 wavelengths are obtained with a signal-to-noise ratio of 35 dB and a wavelength tunability of 10 nm. [ABSTRACT FROM PUBLISHER]

We report high-sensitivity detection of 2,4.6-trinitrotoluene (TNT) by using laser photoacoustic spectroscopy where the laser radiation is obtained from a continuous-wave room temperature high-power quantum cascade laser in an external grating cavity geometry. The external grating cavity quantum cascade laser is continuously tunable over ≈400 nm around 7.3 g≈m and produces a maximum continuous-wave power of ≈200 mW. The IR spectroscopic signature of TNT is sufficiently different from that of nitroglycerine so that unambiguous detection of TNT without false positives from traces of nitroglycerine is possible. We also report the results of spectroscopy of acetylene in the 7.3-µm region to demonstrate continuous tunability of the IR source. [ABSTRACT FROM AUTHOR]

We demonstrate coupled-mode characteristics and bistability in photonic molecule lasers composed of evanescent-coupled GaInAsP twin microdisks. First, we show room-temperature continuous-wave operation by photopumping and discuss the unique behavior of coupled modes, i.e., the anticrossing and splitting characteristics of bonding and antibonding modes. Next, we present the clear bistability, which is observed for the antibonding mode by nonuniform pumping with an effective power of nearly 40 μW. It is explained by rate equation analysis, which assumes saturable absorption. The analysis also predicts mode switching by the carrier-induced refractive index change. A micron-sized device with a very low power consumption will allow large scale integration of optical memories, optical flip-flops, and so forth. [ABSTRACT FROM PUBLISHER]

Optical pulse generation at 100 GHz using a 1.5-μm Fabry-Pe´rot laser is experimentally demonstrated under continuous-wave operation. Although the output from the laser is almost constant, subpicosecond pulses at 100 GHz are obtained after propagation through a single-mode fiber with an adequate anomalous dispersion. The measured radio frequency spectrum confirms that the multiple longitudinal modes of the Fabry-Pe´rot laser are passively mode locked. Mode-locking instabilities appearing as frequency jumps at different currents are observed. [ABSTRACT FROM PUBLISHER]

In this paper, we present a novel Brillouin fiber-ring laser utilizing an unbalanced Mach-Zehnder interferometer (UMZI) as coupling device. The laser is pumped by a distributed-feedback laser diode and shows continuous-wave and single-frequency operation. Frequency-dependent transmission characteristics of the UMZI make it possible for the pump wave to pass through the laser-ring cavity with no resonance effect for stable pump operation, while the Brillouin laser signal still resonates in a high-finesse cavity. Single and multiple longitudinal mode operations are observed according to the relative location between longitudinal modes and Brillouin gain-curve center. A stable single-frequency operation is achieved using a simple stabilizing feedback loop based on dithering and autotracking techniques. Using this simple stabilizing feedback loop, the laser-intensity fluctuation is highly suppressed and remains below 4%. The Brillouin output converted from the pump power of 26.4 mW is about 3.18 mW, and the linewidth is measured to be below 1 kHz. [ABSTRACT FROM PUBLISHER]

The performance characteristics of continuous-wave (CW) InGaN multiple-quantum-well (MQW) laser diodes on copper substrates are reported. InGaN MQW laser diodes (LDs) grown on sapphire substrates by metal-organic chemical vapor deposition were successfully separated from the sapphire and transferred onto copper substrates by using a two-step laser liftoff (LLO) process. Continuous-wave threshold currents as low as 65 mA have been achieved with threshold voltages of 6.5 V with a backside n-contact through the Cu substrate, improved heat dissipation due to the Cu substrate allowed CW laser operation up to a heatsink temperature of 80°C. Significant improvements in light output powers were observed for devices on Cu substrates with maximum CW output power of more than 100 mW [ABSTRACT FROM PUBLISHER]

Continuous-wave (CW) operation of a mid-infrared type-II interband cascade (IC) laser has been demonstrated at temperatures up to 142 K by improving device processing and fabrication. Also, the IC laser exhibited record-high wall-plug efficiencies (~18% at 60 K) with considerable CW output powers. An analysis of the thermal resistance partially explains the still low maximum CW operating temperature and suggests further potential for improvement with continued development of fabrication/packaging techniques [ABSTRACT FROM PUBLISHER]

We present here the design, fabrication, and static as well as dynamic characteristics of a ten-wavelength, 200-GHz channel spacing emitter for wavelength-division multiplexing applications. The source is based on the monolithic integration on InP of a ten distributed Bragg reflector laser array with a square-shaped transmission response PHASAR. The specific design of the PHASAR is detailed. The continuous-wave operation-one channel at a time-demonstrates a high monomode stability with a rejection better than 32 dB for all channels and all injected currents; the 200-GHz channel spacing can be reached with an accuracy better than 25 GHz. High-speed characteristics demonstrate a 6.5-GHz direct modulation bandwidth at -3 dB for a 70-mA current in the 900-μm-long active section. The chirp measured for a 2.5-Gb/s modulation with a 10-dB extinction ratio is less than 1.5 Å for every wavelength [ABSTRACT FROM PUBLISHER]

• The highest CW output power of 1.63 W was obtained in Pr,Mg:SrAl 12 O 19 laser at 643 nm. • The instantaneous output power can be further promoted to 2.32 W by mechanical chopper for thermal mitigation. • Co:ZnSe has been first-time used as saturable absorber in visible at 724 nm. • Passive Q-switched Pr,Mg:SrAl 12 O 19 laser with a maximum average output power of 0.45 W, a pulse width of 180.5 ns, pulse energy of 5 μJ and peak power of 28 W was demonstrated. We report on the recent progress on continuous-wave (CW) and passviely Q-switched Pr,Mg:SrAl 12 O 19 (SRA) bulk lasers using a 24-W diode laser as pump source. Maximum output power of CW laser at 643 nm reached 1.63 W, which is believed to be the highest power that has ever been achieved in diode-pumped Pr3+-doped oxide lasers. After thermal mitigation by a mechanical chopper, a maximum instantaneous output power of 2.32 W can be obtained. For passive Q-switching of Pr,Mg:SRA laser at 724 nm, a Co:ZnSe crystal has been first-time used as saturable absorber, to our knowledge. A maximum average output power of 0.45 W was produced with the shortest pulse width of 180.5 ns at pulse repetition rate of 89.2 kHz, corresponding to pulse energy and peak power of 5 μJ and 28 W. These results indicate that Pr,Mg:SRA is a good oxide candidate for visible laser generation. [ABSTRACT FROM AUTHOR]

A novel fabrication method of buried‐heterostructure (BH) mid‐infrared quantum cascade lasers (QCLs) by using non‐selective regrowth of iron‐doped indium phosphide (InP) (Fe:InP), around deeply etched laser ridges, via metal‐organic chemical vapour deposition (MOCVD) and planarisation via chemical polishing is reported. Owing to better heat dissipation, the fabricated 4.75 μm emitting QCLs exhibit about three‐fold enhancement in maximum output power under continuous‐wave operation at room temperature (T = 20°C) compared with that from lasers without the regrown InP. The demonstrated fabrication method provides a more flexible route to realising BH QCLs by removing strict requirements on the etched‐ridge sidewall profile, as well as on the physical dimensions of the dielectric mask for the regrowth via MOCVD. The method can be further employed for making large‐emitting aperture, closely packed arrays of QCLs, with planarised geometry, for coherent‐power scaling. [ABSTRACT FROM AUTHOR]

Self-sustained pulsation at 65°C under continuous-wave operation was obtained in AlGaInP laser diodes with a saturable-absorbing layer in part of the p-type cladding layer. The carrier overflow was significantly reduced to enable high-temperature performance by increasing the number of well layers in the active layer to four and increasing the compressive strain of the active layer (εact=+0.5%). The effect of the carrier overflow on self-sustained pulsation was investigated by analyzing the lasing spectrum and lasing polarization. The large amount of luminescence from the saturable-absorbing layer demonstrated that excessive carrier overflow at high temperature prevents the saturable absorbing layer functioning as an absorber [ABSTRACT FROM PUBLISHER]

Ridge-waveguide laser diodes emitting near 2.38 μm have been fabricated from GaInAsSb-GaSb type-II quantum-well (QW) structures grown by molecular beam epitaxy. These devices operated continuous-wave (CW) at room temperature, what is obtained for the first time from a type-II QW laser. At 23°C threshold currents in the range 60-140 mA and CW output powers exceeding 1 mW/facet were obtained. These lasers showed a tendency to operate in a single longitudinal mode with a temperature red shift of 0.1 nm/°C and a current red shift of 0.06 nm/mA [ABSTRACT FROM PUBLISHER]

Single mode operation in a wide temperature range (-40°C~+85°C) has been obtained, from an etched-QW strongly gain-coupled (SGC) distributed-feedback laser at 1.3 μm. The SGC lasers exhibit an excellent sidemode-suppression-ratio (SMSR) of around 45-55 dB in continuous-wave operation, and a very good transient SMSR (TSMSR) of more than 35 dB during a gain-switched operation, both are over the entire temperature range. When mounted P-side up, the threshold current is about 12 mA at room temperature and 28 mA at +85°C. The output power is more than 20 mW with only 120-mA injection current at +85°C [ABSTRACT FROM PUBLISHER]

The first room‐temperature operation of a transistor vertical‐cavity surface‐emitting laser (T‐VCSEL) is demonstrated. Fabricated using an epitaxial regrowth process, the T‐VCSEL is electrically a pnp‐type bipolar junction transistor and consists of an undoped AlGaAs/GaAs bottom DBR, an InGaAs triple‐quantum‐well active layer, an Si/SiO2 dielectric top DBR, and an intracavity contacting scheme with three electrical terminals. The output power is controlled by the base current in combination with the emitter‐collector voltage, showing a voltage‐controlled operation mode. A low threshold base‐current of 0.8 mA and an output power of 1.8 mW have been obtained at room temperature. Continuous‐wave operation was performed up to 50°C. [ABSTRACT FROM AUTHOR]

The authors present distributed Bragg reflector (DBR) tapered lasers fabricated on the GaInSb-AlGaAsSb material system. These index guided tapered lasers are equipped with first-order chromium DBRs acting as frequency-selective mirrors on the rear facet. Hence, high-power wavelength stabilized lasers could be realized. The devices exhibit output powers of up to 87 mW and sidemode suppression ratios of 40 dB at an emission wavelength of 2.03 mum in continuous-wave operation. [ABSTRACT FROM PUBLISHER]

An optical memory cell that has four distinctive states, therefore storing 2 bits of information optically, is demonstrated by utilizing a novel single semiconductor microring laser with a retro-reflector cavity. To our best knowledge, it is the first time the combination of two directional and two wavelength states with a single semiconductor ring laser of only 20 times 62 mum2 in size has been demonstrated in which room-temperature continuous-wave operation is realized. These states can be easily written by corresponding optical inputs with low optical energy of ~ 1.56 fJ and rapid access time of ~70 ps suitable for 10 Gb/s or higher data rates. [ABSTRACT FROM PUBLISHER]

The monolithic integration of pump lasers and optically pumped vertical-external-cavity surface-emitting lasers is demonstrated. An innovative contacting scheme for the pump lasers offers high design flexibility and scalability. First devices at 1000 nm generate output powers of 2.5 W in pulsed and 0.65 W in continuous-wave operation. [ABSTRACT FROM PUBLISHER]

The continuous-wave operation, thermal crosstalk measurements, and thermal modeling of a quantum cascade (QC) laser array are presented. Measurements and thermal modeling predict that the thermal crosstalk between array elements can be minimized by improving the heat management when the spacing of neighboring laser elements is greater than 500 mum. The output power of the demonstrated QC laser array significantly exceeds the output power of the individual lasers in the array. This shows the potential of the QC arrays as a candidate for the realization of high-power optical sources in mid-infrared (3-20 mum) spectral range [ABSTRACT FROM PUBLISHER]

We report the wavelength beam combining of an array of high-power high-brightness 970-nm slab-coupled optical waveguide lasers. A 50-W peak power under quasi-continuous-wave (CW) operation was measured in an output beam with a beam quality of Mx,y 2=1.2, and 30 W under CW operation was measured with a beam quality of Mx,y 2=2 [ABSTRACT FROM PUBLISHER]

We have realized compressively strained GaInAsSb-GaSb type-II double quantum-well lasers with an emission wavelength of 2.8 mum. Using broad area devices, an internal absorption of 9.8 cm-1 and an internal quantum efficiency of 0.57 is determined. For the increase of the threshold current with temperature, a T0 of 44 K is obtained. Narrow ridge waveguide lasers show continuous-wave laser operation at temperatures up to 45 degC, with room-temperature (RT) threshold current of 37 mA. At RT, the maximum optical output power per facet of an uncoated 800times7 mum2 ridge waveguide laser exceeds 8 mW [ABSTRACT FROM PUBLISHER]

We report the first experimental demonstration of a novel piezoelectric actuated microelectromechanical systems (MEMS) tunable vertical-cavity surface-emitting laser (VCSEL). A large physical deflection was obtained with the piezoelectric actuated MEMS cantilever beam monolithically integrated with the VCSEL distributed Bragg reflector. Single-mode emission and continuous tuning were achieved at room temperature under continuous-wave operation [ABSTRACT FROM PUBLISHER]

We demonstrate GaN-based high-power single transverse-mode laser diodes (LDs) emitting at 405 nm. LD structures are designed to exhibit a high level of catastrophic optical damage and small beam divergence angle. By the control of refractive index profiles, we achieved a vertical beam divergence angle of as low as 17.5° and maximum output power of as high as 470 mW under continuous-wave operation condition. In addition, nearly fundamental transverse-mode operation is demonstrated up to 500-mW pulsed output power by far-field investigation. [ABSTRACT FROM PUBLISHER]

Sapphire-bonded photonic crystal laser cavities with varying number of photonic crystal periods were studied in order to determine the optical loss in these cavities. The lasing threshold increases as the number of lattice periods decreases, and the quality factors of these cavities were calculated from the lasing threshold data. Continuous-wave operation was achieved for cavities with eight or more cladding periods [ABSTRACT FROM PUBLISHER]

We report an optically pumped vertical external-cavity surface-emitting laser that is designed for emission at two wavelengths simultaneously. Single transverse mode continuous-wave (CW) operation is demonstrated at the wavelengths of 984 and 1042 nm. The device produces a CW optical power of 140 mW for the 984-nm component and 115 mW for the 1042-nm component, exhibiting over 10% efficiency. At a high pump power, self-pulsation of the components appeared on top of the CW-mode components. The maximum total output of 1 W was obtained at the pump power of 9 W. [ABSTRACT FROM PUBLISHER]

We report on the demonstration of continuous-wave (CW) operation of GaInAs-AlGaAsSb quantum cascade (QC) lasers. By placing a 2.5-μm-thick gold layer on both sides of the laser ridge to extract heat from the active region in the lateral direction, together with mounting the device epilayer down, we have achieved CW operation of GaInAs-AlGaAsSb QC lasers composed of 25 stages of active/injection regions. The maximum CW operating temperature of the lasers is 94 K, and the emission wavelength is around λ∼4.65 μm. For a device with the size of 10×2000 μm2, the CW optical output power per facet is 13 mW at 42 K and 4 mW at 94 K. The CW threshold current density is 1.99 kA/cm2 at 42 K, and 2.08 kA/cm2 at 94 K, respectively. [ABSTRACT FROM PUBLISHER]

An uncooled three-section tunable distributed Bragg reflector laser is demonstrated as an athermal transmitter for low-cost uncooled wavelength-division-multiplexing (WDM) systems with tight channel spacing. A ±0.02-nm thermal wavelength drift is achieved under continuous-wave operation up to 70°C. Dynamic sidemode suppression ratio of greater than 35 dB is consistently obtained under 3.125-Gb/s direct modulation over a 20°C-70°C temperature range, with wavelength variation of as low as ±0.2 nm. This indicates that more than an order of magnitude reduction in coarse WDM channel spacing is possible using this source. [ABSTRACT FROM PUBLISHER]

We report continuous-wave (CW) operation of a 4.3-μm quantum-cascade laser from 80 K to 313 K. For a high-reflectivity-coated 11-μm-wide and 4-mm-long laser, CW output powers of 1.34 W at 80 K and 26 mW at 313 K are achieved. At 298 K, the CW threshold current density of 1.5 kA/cm2 is observed with a CW output power of 166 mW and maximum wall-plug efficiency of 1.47%. The CW emission wavelength varies from 4.15 μm at 80 K to 4.34 μm at 298 K, corresponding to a temperature-tuning rate of 0.87 nm/K. The beam full-width at half-maximum values for the parallel and the perpendicular far-field patterns are 26° and 49° in CW mode, respectively. [ABSTRACT FROM PUBLISHER]

We report an electrically pumped vertical-external-cavity surface-emitting laser (VECSEL) that is designed for wafer-scale fabrication. Single-mode continuous-wave operation is demonstrated at a wavelength of 970 nm. The device structure incorporates a curved micromirror output coupler that is produced using a micromolding process. In addition to outlining the VECSEL fabrication process, we quantify its spatial and spectral modal characteristics. [ABSTRACT FROM PUBLISHER]

In0.22Ga0.78As-GaAs quantum-well stripe-geometry and circular ring lasers have been fabricated with pulsed anodic oxidation (PAO). The relationship between ridge heights and laser performance was first studied in the fabrication of stripe lasers. The lowest transparency current density (Jtr) of 61.20 A/cm2 was obtained from the stripe laser with a ridge height of 1.23 μm, corresponding to an etching depth where all the p-doped layers above active region were removed. With the PAO process, when the ridge height (1.77 μm) extended below the active region, Jtr is 76.03 A/cm2, only increased by 24.2%. Based on the experimental results, the circular ring laser, which needs deep etching (below active region) and subsequent PAO, has been fabricated. The fabricated circular ring laser worked under continuous-wave operation at room temperature. Longitudinal mode spacing analysis clearly indicates that the ring resonator is a functional part of the whole circular ring laser. [ABSTRACT FROM PUBLISHER]

We present a compact diode-pumped single-frequency single-polarization erbium-doped fiber laser with fiber Bragg gratings (FBGs) written in the active fiber itself. The single-polarization regime was obtained by applying uni-axial stress to one of the two FBGs forming the cavity. The laser is shown to operate in two regimes-quasi-continuous-wave regime with a few-percent of modulation in the output power and a giant-pulse regime accessible under sinusoidal pump modulation. [ABSTRACT FROM PUBLISHER]

We present the development of novel 980-nm Ga0.8In0.2As-GaAs vertical-cavity surface-emitting lasers (VCSELs) with an internal waveguide structure. The monolithic integration of a horizontal waveguide in the top distributed Bragg reflector (DBR) creates the potential for achieving VCSEL-based photonic integrated circuits. In this work, an AlGaAs-GaAs-AlGaAs waveguide designed for horizontal propagation of light was monolithically integrated as part of the upper GaAs-AlGaAs DBR of the device. VCSELs with 9-μm apertures emitted 3-mW single-mode power with both longitudinal and lateral mode suppression ratio of 40 dB under room-temperature continuous-wave operation. [ABSTRACT FROM PUBLISHER]

This letter presents for the first time an electrically pumped tunable vertical-cavity surface-emitting laser (VCSEL) with a record-breaking tuning range of 40 nm at long wavelengths. The VCSEL is based on a two-chip concept. The laser peak can be tuned continuously and without mode-hopping in a wavelength range above 1.55 μm due to a microelectromechanical movable mirror membrane. The VCSEL is single mode all over the tuning range with a 32-dB sidemode suppression ratio. The laser emits a maximum output power of 100 μW in continuous-wave operation at room temperature. Dynamic measurements of the tuning characteristics show that the 3-dB cutoff frequency for an electrothermal wavelength modulation is about 500 Hz and the 1/e-time constant of the step response is about 1 ms. [ABSTRACT FROM PUBLISHER]

Electrically pumped buried tunnel junction InGaAlAs-InP vertical-cavity surface-emitting lasers (VCSELs) with self-adjusted lateral current and optical confinement and record emission wavelengths beyond 2 μm are presented. Front and back side mirrors are realized using 31.5 epitaxial layer pairs of alternating InGaAs-InAlAs and a dielectric 2.5 pair CaF2-a-Si layer stack. The devices show single-mode continuous-wave operation up to heat sink temperatures over 80°C. The maximum output power at 20°C reaches 0.43 mW, threshold current and voltage are as low as 0.66 mA and 0.73 V, respectively. To reach the long emission wavelength, we use an optimized active region comprising heavily strained quantum wells. High-resolution X-ray diffraction and photoluminescence measurements reveal excellent material quality without relaxation in the quantum wells. [ABSTRACT FROM PUBLISHER]

We present a procedure for determining the linewidth enhancement factor (α parameter) in semiconductor lasers under continuous-wave (CW) operation. It is based on the measurement of the amplified spontaneous emission spectra, with a proper correction of thermal effects. The method is applied to 735-nm tensile strained GaAsP-AlGaAs quantum-well lasers and it is validated by comparing CW results, after correcting thermal effects, with pulsed measurements. The results show a low value of the α parameter attributed to the tensile strain. [ABSTRACT FROM PUBLISHER]

The long-term stability of high-brightness diode lasers at 735 nm was investigated. The diodes consist of an index-guided straight section and a gain-guided tapered section. A 1-W continuous-wave operation for 2-mm-long tapered lasers over 3200 h is reported. The experiments demonstrate high reliability with degradation rates below 3.2×10-5 h-1. [ABSTRACT FROM PUBLISHER]

In this letter, we present the first demonstration of a long wavelength-tunable vertical-cavity surface-emitting laser (VCSEL) using a monolithically integrated bridge tuning microelectromechanical system structure. The use of such a tuning structure allows for better wavelength tuning repeatability and wider tuning range as compared to cantilever-based tunable VCSELs. The devices show tuning ranges over 22 nm with peak output power of 1.3 mW in continuous-wave operation at 15°C. The bridge structure has a mechanical resonant frequency of 80 kHz. The transmission test through 300-km single-mode fiber (SMF-28) using the tunable VCSEL under mechanical vibration below 10 KHz and 10-G acceleration shows little bit-error-rate degradation. [ABSTRACT FROM PUBLISHER]

We report continuous-wave (CW) operation of quantum-cascade lasers (λ=6 μm) up to a temperature of 313 K (40°C). The maximum CW optical output powers range from 212 mW at 288 K to 22 mW at 313 K and are achieved with threshold current densities of 2.21 and 3.11 kA/cm2, respectively, for a high-reflectivity-coated 12-μm-wide and 2-mm-long laser. At room temperature (298 K), the power output is 145 mW at 0.87 A, corresponding to a power conversion efficiency of 1.68%. The maximum CW operating temperature of double-channel ridge waveguide lasers mounted epilayer-up on copper heatsinks is analyzed in terms of the ridge width, which is varied between 12 and 40 μm. A clear trend of improved performance is observed as the ridge narrows. [ABSTRACT FROM PUBLISHER]

GaInAsSb-AlGaAsSb multiple quantum-well (QW) lasers with an emission wavelength of 2.81 μm are reported. The ridge waveguide lasers with highly strained QWs show continuous-wave laser emission up to 25°C; in pulsed mode, the lasers operate up to 60°C. For pulsed operation, a threshold current density of 360 A/cm2 is found for devices with 30-μm stripe width and 2-mm cavity length at room temperature. A low threshold current density at infinite length of 248 A/cm2 is derived. [ABSTRACT FROM PUBLISHER]

We demonstrate continuous-wave operation and passive mode locking of extended cavity lasers fabricated in 1.3-μm InAlGaAs strained multiple quantum-wells structure. Modal losses were measured for the passive section fabricated by quantum-well intermixing. Pulse duration of 1.7 ps was deduced from intensity autocorrelation measurement. [ABSTRACT FROM PUBLISHER]