Search

In this paper, an adiabatic operation slope-loss algorithm (AO-SLA) is developed for designing efficient adiabatic waveguide tapers. The algorithm can compute the efficient adiabatic guided-wave shape of the waveguide taper. A well-studied case of an adiabatic waveguide taper is used to show how it can readily generate a guided-wave shape that gives the same mode-connection power transfer with a much shorter length compared with the linear shape. In the waveguide taper design, it is shown that the device efficiency designed with AO-SLA is better than that based on the parabolic case and the SLA case, and the adiabatic taper designed can give a broad operating bandwidth. Moreover, the adiabatic condition α for AO-SLA can be very large.

We report the designs of on-chip grating couplers for the silicon hybrid plasmonic waveguides, which is the first proposal, to the best of our knowledge, for the direct coupling between a standard single-mode fiber and a hybrid plasmonic waveguide. By leveraging the apodized gratings and a two-stage-taper mode converter, we obtain a theoretical coupling efficiency of 79% (−1.03 dB) at the 1550 nm wavelength and a 3-dB bandwidth of 73 nm between the fiber and a 100 nm-wide silicon hybrid plasmonic waveguide with a bottom metal layer. We further propose grating couplers for three other sorts of silicon hybrid plasmonic waveguides with a metal cap and theoretically achieve good performances with coupling efficiencies larger than 47% and bandwidths larger than 51 nm. The proposed direct coupling scheme can avoid extra insertion losses and additional alignment processes that conventional indirect coupling schemes produce. It is believed to be a new step forward to the CMOS-compatible and large-scale integration based on the plasmonic waveguides. [ABSTRACT FROM AUTHOR]

We report the designs of on-chip grating couplers for the silicon hybrid plasmonic waveguides, which is the first proposal, to the best of our knowledge, for the direct coupling between a standard single-mode fiber and a hybrid plasmonic waveguide. By leveraging the apodized gratings and a two-stage-taper mode converter, we obtain a theoretical coupling efficiency of 79% (−1.03 dB) at the 1550 nm wavelength and a 3-dB bandwidth of 73 nm between the fiber and a 100 nm-wide silicon hybrid plasmonic waveguide with a bottom metal layer. We further propose grating couplers for three other sorts of silicon hybrid plasmonic waveguides with a metal cap and theoretically achieve good performances with coupling efficiencies larger than 47% and bandwidths larger than 51 nm. The proposed direct coupling scheme can avoid extra insertion losses and additional alignment processes that conventional indirect coupling schemes produce. It is believed to be a new step forward to the CMOS-compatible and large-scale integration based on the plasmonic waveguides.

In this letter we present new results on high power 970 nm ridge waveguide lasers based on an extreme double asymmetric epitaxial design. Due to an improved lateral-longitudinal design an M2-value below 1.1 and efficiency over 60% could be maintained at power levels slightly above 2 W. The lasers consist of a narrow mode-filter section at the back facet, a relatively broad section at the front facet for high power capability, and a tapered section in between with a very small taper-angle. We achieved the highest reported conversion efficiency for 1 W single lateral mode power to date of 67%, as well as the highest lateral (linear) brightness of 7.5 W/mm ⋅ mrad with 55% efficiency at 2.5 W. Results of first life time tests are presented which show the potential for commercial use. [ABSTRACT FROM AUTHOR]

Low-cost, high-performance integration technologies are instrumental for active–passive integrated photonics devices. The monolithic integration of Al2O3 and Si3N4 is studied, enabling to combine the promising optical features of Si3N4 with the excellent optical gain characteristics of rare-earth-ion doped Al2O3. The Al2O3 and Si3N4 layers are separated by a thin SiO2 film and coupled by adiabatically width-tapered Al2O3 and thickness-tapered Si3N4 waveguides. In this paper, a detailed characterization of the couplers, as well as a study of the influence of the different design parameters and fabrication tolerances on the final device performance is presented. Test structures are characterized under transverse electric (TE) polarization. Measured loss per coupler is as low as 0.26 ± 0.03 dB at the wavelength of 1030 nm, and below 0.24 dB in the spectral window of 1460–1635 nm. Lateral misalignment of ±1 μm results in less than 0.6 dB increase of the coupler loss at 1030 nm, and the tolerance of misalignment goes up to 1.7 μm at the investigated longest wavelength of 1635 nm without introducing extra coupler losses. The reported integration technology paves the way toward a double-layer platform monolithically integrating Si3N4 and rare-earth-ion doped Al2O3 for active–passive photonic functionalities. [ABSTRACT FROM AUTHOR]

Abstract: A dual‐polarization 10‐channel mode (de)multiplexer is proposed and realized with cascaded dual‐core adiabatic tapers on a silicon‐on‐insulator (SOI) platform. The mode demultiplexer has a 2.3 μm‐wide multimode bus waveguide, which supports six mode‐channels of TE polarization and four mode‐channels of TM polarization. These ten mode‐channels are (de)multiplexed with five cascaded dual‐core adiabatic tapers based on SOI nanowires. The widths for these dual‐cores are chosen optimally according to the dispersion curves of the dual‐core SOI nanowire, so that the desired highest‐order modes of TE‐ and TM‐polarizations are extracted simultaneously. These two extracted mode‐channels are coupled very efficiently to the fundamental modes of TE‐ and TM‐polarizations (TE0 and TM0) in the narrow waveguide, respectively, which are then separated by using a polarization beam splitter based on bent directional couplers. A chip consisting of a pair of 10‐channel mode (de)multiplexers is fabricated and then tested with data transmission of 30Gbps/channel. The measurement results show that all TM‐ and TE mode‐channels have low crosstalks (–15∼–25 dB) and low excess losses (0.2∼1.8 dB) over a broad wavelength band of ∼90 nm, which makes it WDM (wavelength‐division‐multiplexing)‐compatible and thus suitable for high capacity on‐chip optical interconnects. [ABSTRACT FROM AUTHOR]

A polarization splitter-rotator (PSR) based on the supermode evolution in a dual-core adiabatic taper with multiple segments is designed. For this dual-core adiabatic taper, one core becomes narrow and the other one becomes wide. The gap between them is kept constant except the input/output parts where these dual cores are separated gradually. When choosing some specific widths for the dual cores, mode hybridization between the TM0 supermode and the TE 1 supermode happens. As a result, when light propagates along the dual-core adiabatic taper, the TM0 supermode launched from the input port can be efficiently converted to the TE1 supermode, which is mainly confined in the core connected to the cross port, and finally one has the TE0 mode output from the cross port. On the other hand, the TE0 mode launched from the input port is confined tightly in the core connected to the through port and finally outputs from the through port with a very low loss. For the structural design of the adiabatic taper, three operation wavelengths of 1450, 1550, and 1650 nm are considered simultaneously so that the PSR works well in a very broad band from 1450 to 1650 nm. Here, the widths of the multiple segments in the taper section are chosen optimally according to the mode hybridization regions of the dual-core waveguide when operating at the wavelengths of 1450, 1550, and 1650 nm. With this design method, the designed PSR based on silicon-on-insulator nanowires is about 240 μm long. The bandwidth is even as large as 300 nm (1450–1750 nm) for an extinction ratio of >16 dB and an excess loss of <0.1 dB in theory. [ABSTRACT FROM PUBLISHER]

We demonstrate a refractive index sensor based on a long period grating (LPG) inscribed in a special photosensitive microfiber with double-clad profile. The fiber is tapered gradually enough to ensure the adiabaticity of the fiber taper. In other words, the resulting insertion loss is sufficiently small. The boron and germanium co-doped inner cladding makes it suitable for inscribing gratings into its tapered form. The manner of wavelength shift for refractive indices (RIs) differs from conventional LPG, and the refractive index detection limit is 1.67 × 10−5.

We demonstrate a refractive index sensor based on a long period grating (LPG) inscribed in a special photosensitive microfiber with double-clad profile. The fiber is tapered gradually enough to ensure the adiabaticity of the fiber taper. In other words, the resulting insertion loss is sufficiently small. The boron and germanium co-doped inner cladding makes it suitable for inscribing gratings into its tapered form. The manner of wavelength shift for refractive indices (RIs) differs from conventional LPG, and the refractive index detection limit is 1.67 x 10-5. [ABSTRACT FROM AUTHOR]

A new cavity design for the clad-pumped fiber laser (CPFL) was proposed and experimentally demonstrated in a Nd-doped silica fiber with the single transverse mode output and an enhancement in the slope efficiency for butt-coupled end pumping. In a fiber cavity two concatenated adiabatic rectangular tapers were formed to remove the optical feedback in higher order modes as well as to provide a low splice loss to standard single mode fibers. Mode propagation along the composite cavity was theoretically analyzed using beam propagation method and continuous wave oscillation in the LP01 mode at 1.06 μm was achieved with the output power over 1.3 W at the pump power of 3.67 W. [Copyright &y& Elsevier]

A novel on-chip ultra-broadband polarization splitter–rotator (PSR) based on an inverse asymmetrical ridge taper coupler is proposed by using evanescent coupling between two straight waveguides with gradual ridge widths. The two ridge-widths decrease inversely to realize mode hybridization between fundamental transverse magnetic (TM 0) mode and fundamental transverse electric (TE 0) mode, which effectively expands the bandwidth. The structural parameters are optimized by utilizing the frequency-domain finite-difference and eigenmode expansion method. The results show that efficient polarization splitting and rotating are simultaneously achieved with a broad operating bandwidth from 1250 nm to 1750 nm and a high polarization conversion efficiency of more than 95%. The insertion loss is below 0.05 dB and 0.2 dB over the bandwidth for TE 0 and TM 0 , respectively. To the best of our knowledge, the PSR achieves the broadest bandwidth up to 500 nm (covering all the optical fiber communication O-, E-, S-, C-, L-, and U-bands) for the first time. • A polarization splitter–rotator is proposed utilizing inverse asymmetrical ridge taper structure. • Proposed PSR deliver great performance with a operating bandwidth from 1250 nm to 1750 nm. • The design of device is CMOS compatible and suitable for integration in high performance PICs. [ABSTRACT FROM AUTHOR]

We report on a heterogeneously integrated InP/silicon-on-insulator (SOI) laser source realized through divinylsiloxane-bis-benzocyclobutene (DVS-BCB) wafer bonding. The hybrid lasers present several new features. The III-V waveguide has a width of only 1.7 μm, reducing the power consumption of the device. The silicon waveguide thickness is 400 nm, compatible with high-performance modulator designs and allowing efficient coupling to a standard 220-nm high index contrast silicon waveguide layer. In order to make the mode coupling efficient, both the III-V waveguide and silicon waveguide are tapered, with a tip width for the III-V waveguide of around 800 nm. These new features lead to good laser performance: a lasing threshold as low as 30 mA and an output power of more than 4 mW at room temperature in continuous-wave operation regime. Continuous wave lasing up to 70°C is obtained. [ABSTRACT FROM PUBLISHER]