ARROW-type polarizer utilizing form birefringence in multilayerfirst cladding

A waveguide polarizer using an ARROW (antiresonant reflecting optical waveguide) structure, of which the first cladding consists of three thin layers, is proposed. Theoretical calculation shows that this polarizer can achieve isolation over 30 dB/cm with an insertion loss of 0.01 dB/cm at 1.3 μm. Isolation of 83 dB/cm with insertion loss of 4.3 dB/cm was experimentally obtained at 0.633 μm. This structure is suitable for the integration of a polarization splitter and photodetector     

Mode locking of a Nd:YAlO3 laser at 1.08 and 1.34 μmwavelengths using a single LiIO3 crystal

Passive mode locking of a Nd:YAlO₃ laser at 1.08 and 1.34 μm using a nonlinear mirror based on second harmonic generation is described. A single 30° cut frequency-doubling LiIO₃ crystal was used to mode lock both transitions, demonstrating the superiority of this mode-locking technique over that using saturable absorbers. Pulses as short as 50 ps at 1.08 μm and 15 ps at 1.34 μm were obtained. A comparative analysis of the mode-locking performance at the two fundamental wavelengths is presented, indicating that the longer pulse duration at 1.08 μm is due to the higher gain and an insufficient number of round-trips in the pulse train development     

Elimination of polarization sensitivity in silica-based wavelengthdivision multiplexer using a polyimide half waveplate

This paper proposes a low-loss technique for eliminating polarization sensitivity in a silica-based planar lightwave circuit (PLC) which uses a polarization mode converter formed at the center of the circuit. This converter consists of a waveguide gap housing a polyimide half waveplate. The excess loss of the converter was drastically reduced to 0.26 dB with a Δ=0.75% waveguide by employing an 18 μm-wide waveguide gap and a 14.5 μm-thick polyimide half waveplate. A polarization mode conversion crosstalk of -37 dB was achieved at 1.55 μm. Using this converter, we successfully eliminated the polarization sensitivity in some silica-based PLC-type wavelength division multiplexers. The converter is also insensitive to temperature and offers long term stability     

2×2 fused fiber null couplers with asymmetric waist crosssections for polarization independent (<0.01 dB) switching

Polarization independent (<0.01 dB) switching is achieved at 1.55 μm in a strongly guiding, fused tapered fiber null coupler acoustooptic switch. An intermediate degree of fusion of the dissimilarly sized fibers is shown experimentally to have the form birefringence required to render the mode-splitting coupler polarization insensitive. The effect of the degree of fiber fusion on the acoustic wavelength of flexural waves is studied theoretically and experimentally, and precise control over the degree of fiber fusion is obtained for coupler waist cross-sectional dimensions as small as 6 μm     

A high-resolution and high-speed ferroelectric liquid-crystalshutter array print head

A 1-in-wide, 577-dot/in, and 4:1 multiplex ferroelectric-liquid-crystal (FLC) shutter array has been fabricated and tested for optical performance. The array has a cell gap of 2.8 μm and is surface stabilized with an FLC material of high spontaneous polarization (140 nC/cm²) and fast switching time (16 μs) at room temperature. It is capable of operating at a speed of 6.5 in/s (24 p.p.m. printing speed) with optical contrast ratios of better than 4. Using tungsten-halogen illumination, a prototype print head has been made, and print samples have been obtained on an electrophotographic printer engine     

A room temperature 0.1 μm CMOS on SOI

An advanced 0.1 μm CMOS technology on SOI is presented. In order to minimize short channel effects, relatively thick nondepleted (0.15 μm) SOI film, highly nonuniform channel doping and source-drain extension-halo were used. Excellent short channel effects (SCE) down to channel lengths below 0.1 μm were obtained. It is shown that undepleted SOI results in better short channel effect when compared to ultrathin depleted SOI. Devices with little short channel effect all the way to below 500 Å effective channel length were obtained. Furthermore, utilization of source-drain extension-halo minimizes the bipolar effect inherent in the floating body. These devices were applied to a variety of circuits: Very high speeds were obtained: Unloaded delay was 20 ps, unloaded NAND (FI=FO=3) was 64 ps, and loaded NAND (FI=FO=3, C_L=0.3 pF) delay was 130 ps at supply of 1.8 V. This technology was applied to a self-resetting 512 K SRAM. Access times of 2.5 ns at 1.5 V and 3.5 ns at 1.0 V were obtained     

1.55-μm polarization-insensitive optical amplifier withstrain-balanced superlattice active layer

A polarization insensitive (sensitivity <1 dB) GaInAs-GaInAsP semiconductor optical amplifier has been realized at 1.55 μm. The active layer consists of a strain-balanced superlattice structure. Gain polarization insensitivity on a large bandwidth (60 nm) together with a 22.5-dB signal gain and a 11-dBm polarization-insensitive saturation output power are obtained     

Sub-100 fs Kerr lens modelocked Cr4+:YAG laser

Sub-100 fs pulse generation from a Kerr lens modelocked Cr⁴⁺ :YAG laser has been demonstrated for the first time, yielding femtosecond pulses tunable from 1.49 to 1.56 μm with pulses as short as 90 fs obtained at 1.53 μm     

Ultracompact multimode interference 3-dB coupler with stronglateral confinement by deep dry etching

Extremely short InP-InGaAsP MMI 3-dB couplers (L~15-50 μm) with conventional structure have been successfully fabricated. The significant size reduction was achieved by deep dry etching and tapered access waveguide with large S-bend design. Optical transmission measurements on these devices have been performed. An optical bandwidth about 80 nm with a limit of 2-dB excess loss was obtained for most of the couplers. During the whole tunable wavelength range (λ~1485-1580 nm), the imbalance is within ±0.5 dB. Fabrication tolerance and polarization independence are also investigated and the results demonstrated the applicability of these ultracompact devices in high-density photonic integrated circuit     

Broad-band array multiplexers made with silica waveguides onsilicon

A waveguide array multiplexer design that is particularly suitable for making broadband low-order devices is presented. Two-channel multiplexers at 1.0-1.55 μm, 1.31-1.53 μm, and 1.47-1.55 μm are demonstrated. Compared to conventional waveguide multiplexers, these devices have wide spectral ranges of low crosstalk. The devices are polarization independent. The crosstalk and fiber-to-fiber insertion loss for the 1.31-1.53 μm multiplexer were about -35 and -2 dB, respectively     

Proposal and analysis of an ultrashort directional-couplerpolarization splitter with an NLC coupling layer

We propose a novel, high-performance directional-coupler polarization splitter using a nematic liquid crystal (NLC) as the coupling layer. The beam propagation method is used to investigate the propagation characteristics of the device under various conditions. Results of numerical calculations relevant to the design conditions are presented. Because of the large birefringence of NLC, a very short device length of 140 μm is achievable at a high extinction ratio of 28 dB     

Fluorescence and laser operation in single-mode Ti-diffusedNd:MgO:LiNbO3 waveguide structures

The spectral properties of the guided-wave Nd fluorescence and results of laser oscillation in Ti-indiffused single-mode Nd:MgO:LiNbO ₃ waveguides and waveguide cavities, respectively, are reported. The splitting and polarization behavior of the fluorescence lines around 0.9, 1.08, and 1.37 μm were studied. Using a single-mode diode laser as a pump source (λ_p=814.6 nm), an oscillation threshold in an 8-mm-long structure of 2.1-mW absorbed pump power has been obtained. An output power up to 310 μW (limited by the available pump power), a slope efficiency of 16% at power levels >150 μW, and an emission linewidth of 0.21 nm (at λ_s=1085 nm) have been measured     

Highly doped InGaP/InGaAs/GaAs pseudomorphic HEMT's with 0.35 μmgates

We fabricated 0.35-μm gate-length pseudomorphic HEMT DCFL circuits using a highly doped thin InGaP layer as the electron supply layer. The InGaP/InGaAs/GaAs pseudomorphic HEMT grown by MOVPE is suitable for short gate-length devices with a low supply voltage since it does not show short channel effects even for gate length down to 0.35 μm. We obtained a K value of 555 mS/Vmm and a transconductance g_m of 380 mS/mm for an InGaP layer 18.5 nm thick. Fabricated 51-stage ring oscillators show the basic propagation delay of 11 ps and the power-delay product of 7.3 fJ at supply voltage of V_DD of 1 V, and 13.8 ps and 3.2 fJ at V_DD of 0.6 V for gates 10 μm wide     

Single-transverse mode and stable-polarization operation underhigh-speed modulation of InGaAs-GaAs vertical-cavity surface-emittinglaser grown on GaAs (311) B substrate

We have demonstrated an oxide confinement vertical-cavity surface-emitting laser grown on a GaAs (311)B substrate, and achieved single-transverse mode and single-polarization operation in the entire tested current range. The threshold was 0.6 mA for a 2.7 μm×2.9 μm oxide aperture. Even under high-speed modulation up to 5 GHz, the device showed stable single-transverse mode and polarization. Sidemode suppression ratio and orthogonal polarization suppression ratio were over 30 and 10 dB, respectively     

A 1.3 μm directional coupler polarization splitter by ionexchange

A glass waveguide polarization splitter for operation in the 1.3 μm wavelength region is reported. The device, which has a symmetric directional coupler configuration, exploits the stress-induced birefringence in K⁺-Na⁺, ion-exchanged waveguides, giving rise to an adequate difference in the coupling lengths for the two polarizations. Starting from the measured potassium concentration (refractive index) profile of the structure and utilizing a combination of the multilayer stack theory and the effective-index method, the normal mode propagation constants and mode field profiles are calculated to determine the polarization splitting length and the extinction ratio, and the results are compared with the experimental data. It is shown that in a given coupler, the splitting occurs at several wavelengths in the 1.0-1.45 μm range. A 25 mm-long coupler, fabricated by thermal diffusion of K⁺ ions in BK7 glass, exhibits an extinction ratio of 18.2 dB at 1.32 μm, in excellent agreement with the simulation results     

Beam magnification and the efficiency of optical trapping with790-nm AlGaAs laser diodes

The efficiency of dielectric particle confinement with 790 nm AlGaAs laser diode optical traps is investigated as a function of beam magnification and polarization state. When an anamorphic prism pair is used to correct for diode beam ellipticity, trapping efficiencies of nearly 0.37 are achieved with a magnification factor of 3×, laser powers of 4-18 mW, and an overfilled microscope objective entrance aperture. Results are compared for diodes having small (8 μm) and large (57 μm) astigmatisms, but comparable far-field divergence angles     

Visible AlGaAs single quantum well lasers with low thresholdcurrent density grown by molecular beam epitaxy

The letter reports short wavelength emission (7205 Å) from MBE AlGaAs GRINSCH single quantum well lasers. Visible emission is obtained with a 60 Å AlGaAs well containing ≃18% aluminium and both design optimisation and growth conditions lead to low-threshold operation. Broad area Fabry-Perot diodes have threshold current densities as low as 390 A/cm² and 670 A/cm² for cavity lengths of 500 μm and 250 μm, respectively     

Mid-infrared fluoride fiber lasers in multiple cascade operation

CW fiber laser cascades in an Er³⁺-doped fluorozirconate fiber operating simultaneously at 2.7 μm/1.55 μm or at 3.45 μm/2.7 μm/1.55 μm pumped around 650 nm are reported. Output powers of nearly 20 mW at 1.55 μm and 1.2 mW around 2.7 μm were obtained with a nonoptimized experimental setup for the 2.7 μm/1.55 μm cascade. At 1.55 μm a laser efficiency of 5% was achieved. By varying the parameters of the experimental setup, additional effective simultaneous laser action at 3.45 μm was demonstrated     

Extremely low threshold (0.56 mA) operation in 1.3 μmInGaAsP/InP compressive-strained-MQW lasers

A record low threshold current of 0.56 mA, as a long-wavelength laser, has been obtained in a 1.3 μm InGaAsP/InP strained-MQW laser, at room temperature (25°C), by optimising an active layer and by employing a short cavity with high-reflection coatings     

Submicron-square emitter AlGaAs/GaAs HBTs with AlGaAshetero-guardring

Successful operation of submicron-square emitter AlGaAs/GaAs HBTs is demonstrated for the first time by using a fully mesa-structure-type emitter-base junction-area definition method with an AlGaAs hetero-guardring. The hetero-guardring reduces surface recombination current at the emitter-mesa edge to 1.4 μA/μm. This is 1/10 of that for devices without the guardring. Here, dc gains of 20, 26, and 40 are achieved for 0.5 μm×0.5 μm, 0.7 μm×0.7 μm, and 0.9 μm×0.9 μm emitter HBTs, respectively. An f_T of 40 GHz, and an f_max of 30 GHz are obtained for 0.9 μm×0.9 μm at a J_C of 1.0×10⁵ A/cm²