High-performance long-wavelength (λ~1.3 μm) InGaAsPNquantum-well lasers

We demonstrate high-performance InGaAsPN quantum well based long-wavelength lasers grown on GaAs substrates, nitrogen containing lasers emitting in the λ=1.2- to 1.3-μm wavelength range were grown by gas source molecular beam epitaxy using a RF plasma nitrogen source. Under pulsed excitation, lasers emitting at λ=1.295 μm exhibited a record low threshold current density (J_TH) of 2. 5 kA/cm². Lasers grown with less nitrogen in the quantum well exhibited significantly lower threshold current densities of J_TH =1.9 kA/cm² at λ=1.27 μm and J_TH=1.27 kA/cm² at λ=1.2 μm. We also report a slope efficiency of 0.4 W/A and an output power of 450 mW under pulsed operation for nitrogen containing lasers emitting at 1.2 μm     

High T0 long-wavelength InGaAsN quantum-well lasersgrown by GSMBE using a solid arsenic source

We demonstrate high performance, λ=1.3- and 1.4-μm wavelength InGaAsN-GaAs-InGaP quantum-well (QW) lasers grown lattice-matched to GaAs substrates by gas source molecular beam epitaxy (GSMBE) using a solid As source. Threshold current densities of 1.15 and 1.85 kA/cm² at λ=1.3 and 1.4 μm, respectively, were obtained for the lasers with a 7-μm ridge width and a 3-mm-long cavity. Internal quantum efficiencies of 82% and 52% were obtained for λ=1.3 and 1.4 μm emission, respectively, indicating that nonradiative processes are significantly reduced in the quantum well at λ=1.3 μm due to reduced N-H complex formation. These Fabry-Perot lasers also show high characteristic temperatures of T₀ =122 K and 100 K at λ=1.3 and 1.4 μm, respectively, as well as a low emission wavelength temperature dependence of (0.39±0.01) nm/°C over a temperature range of from 10°C to 60°C     

Improved catastrophic optical mirror damage level in InGaAs/AlGaAslaser diodes

9.2 W continuous wave (CW) optical power at a heatsink temperature 10°C and 12.2 W in a regime with stabilised temperature of the laser chip is demonstrated from a 100 μm aperture InGaAs/AlGaAs (λ=1.03 μm) laser diode with 0.4 μm wide GaAs waveguide. Thus, record-high optical power densities of 30 MW/cm² and 40 MW/cm² correspondingly are achieved at the front facet without catastrophic optical mirror damage (COMD)     

Single-mode fibres with extremely high-Δ and small-dimensionpure GeO2 core for efficient nonlinear optical applications

Single-mode fibres with 8.2% Δ and a 1.4 μm diameter-GeO ₂ core have been prepared for efficient stimulated Raman effect. When pumping a 2.7 m-long fibre by a Q-switched and mode-locked Nd:YAG laser (λ=1.064 μm), the first Stokes light (λ=1.114 μm) and second Stokes light (λ=1.169 μm) have been observed at the input peak power levels of 24 W and 40 W, respectively. These results indicate that the above critical power levels are approximately 10^-2~10^-3 smaller than those for the high-silica single-mode fibre     

Si-based receivers for optical data links

We present results for Ge_xSi_1-x waveguide pin detectors grown by rapid thermal chemical vapor deposition (RTCVD). Detectors with multiple Ge_0.29Si_0.71 absorption layers show an internal quantum efficiency of 33% at λ=1.3 μm with a dark current of 27 pA/μm². The external quantum efficiency is limited to 7% by the fiber-to-waveguide coupling efficiency. The output eye diagram for a hybrid λ=1.3 μm silicon receiver at 500 Mb/s is demonstrated. Prospects of a silicon-based optoelectronic receiver array technology are discussed     

Guided-wave optical equalizer with α-power chirped grating

A theoretical investigation of a guided-wave optical equalizer with an α-power chirped grating is presented. A group delay dispersion of 3700 ps/nm can be obtained at λ=1.55 μm by a chirped grating with α=0.3. It is shown that the chromatic dispersion of 200 km of a fiber whose zero-dispersion wavelength is located at 1.3 μm can be compensated at 1.55 μm to achieve up to 10 GHz signal bandwidth     

Monolithic integration of optoelectronic devices with reactivematching networks for microwave applications

Microwave impedance matching networks have been, for the first time, monolithically integrated with GaInAs p-i-n photodiodes and GaInAsP buried ridge stripe structure lasers (λ=1.3 μm), both on a semi-insulating InP substrate. The microwave power transfer optical links were compared using matched and unmatched devices. Compared to an unmatched link, an improvement of 11.4 dB at 5.6 GHz (600 MHz bandwidth) is obtained for the totally matched one; this result corresponds quite well to the theoretical prediction (12 dB at 6 GHz)     

Low-threshold current, high-efficiency 1.3-μm wavelengthaluminum-free InGaAsN-based quantum-well lasers

We demonstrate high-performance Al-free InGaAsN-GaAs-InGaP-based long-wavelength quantum-well (QW) lasers grown on GaAs substrates by gas-source molecular beam epitaxy using a RF plasma nitrogen source. Continuous wave (CW) operation of InGaAsN-GaAs QW lasers is demonstrated at λ=1.3 μm at a threshold current density of only J_TH =1.32 kA/cm². These narrow ridge (W=8.5 μm) lasers also exhibit an internal loss of only 3.1 cm^-1 and an internal efficiency of 60%. Also, a characteristic temperature of T₀=150 K from 10°C to 60°C was measured, representing a significant improvement over conventional λ=1.3 μm InGaAsP-InP lasers. Under pulsed operation, a record high maximum operating temperature of 125°C and output powers greater than 300 mW (pulsed) and 120 mW (CW) were also achieved     

Optical channel waveguide in chalcogenide (Ga:La:S) glass

A novel method for fabricating optical channel waveguides in Ga:La:S chalcogenide glass, through continuous wave direct UV laser writing (λ=244 nm) is reported. Well-formed single-mode channel structures, with low propagation losses of 0.38±0.05 dB/cm at 1.3 μm, were engineered using this technique     

High-performance undoped InP/n-In0.53Ga0.47AsMSM photodetectors grown by LP-MOVPE

A new high-performance undoped In_0.53Ga_0.47As metal-semiconductor-metal photodetector (MSM-PD) with an undoped InP barrier-enhancement layer is reported. The layers were grown by the low-pressure metalorganic vapor-phase epitaxy (LP-MOVPE) technique. The main features of this device include: a very low dark current of less than 60 nA, (100×100) μm², at 1.5 V; a short risetime of 30 ps at 6 V; and a high responsivity of 0.42 A/W for λ=1.3 μm     

Leaky mode propagation in planar multilayer birefringentwaveguides: longitudinal dielectric tensor configuration

In this paper we examine leaky mode propagation in a general five-layered c-rotated optical structure with longitudinal dielectric tenser configuration that can be considered a useful pattern for many actual waveguides. The dependence of the leaky mode propagation on the longitudinal angle φ (between the optical c-axis and laboratory axis) is shown and the dispersion characteristics for different types and thicknesses of buffer and metal layer are reported. The guided mode losses at the wavelength λ=0.633 μm assume the lowest values (about 1 dB/cm) for an Ag layer and for φ=0°. Furthermore, we investigate the variation in the propagation characteristics of the leaky and guided modes with respect to the source wavelength. We obtain the transition wavelength from (G) guided modes to lowest order (L¹ ) leaky mode, having the ordinary component that leaks into the substrate; the transition wavelength to a higher order (L²) leaky mode, which has both ordinary and extraordinary leaky components and the leaky cutoff wavelength. As an example, for φ=10° and an Ag metal layer, the first-order G₁₁ mode transforms from guided to leaky L₁₁¹ at λ_gl≃0.9 μm. The losses exhibit a change of several dB near the wavelength transition from guided to leaky mode (e.g. The attenuation constant of the G₁₁ mode changes from 0.26×10² dB/cm at λ=0.633 μm to 0.18×10 ⁵ dB/cm at λ=0.95 μm where its ordinary component is a leaky one). A similar change is found near the transition wavelength from a lowest-order mode to the highest-order leaky mode     

Vertically integrated silicon-on-insulator waveguides

A SiO₂-Si-SiO₂-Si-SiO₂-Si structure produced by the separation by implantation of oxygen (SIMOX) process used for dual vertically integrated waveguiding in silicon at λ=1.3 μm is discussed. Independent waveguiding is observed when 2-μm-thick Si cores are separated by 0.36-μm-thick SiO₂ . Coupled waveguiding is found for an 0.12-μm intercore oxide thickness     

Analysis of temperature dependent optical gain of strained quantumwell taking account of carriers in the SCH layer

The temperature dependence of optical gain in strained quantum well is analyzed taking account of carriers in the separate confinement heterostructure (SCH) layer. Taking account of these carriers in the SCH layer can explain to a considerable extent the difference in the temperature performance between the λ=0.98 μm laser and λ=1.3 μm laser. It is shown that well depth plays a crucial role for the temperature dependence of optical gain. A strained quantum well on an InGaAs ternary substrate is shown to give a high gain with a small temperature dependence     

High-speed bulk InGaAsP-InP electroabsorption modulators withbandwidth in excess of 20 GHz

Bulk InGaAsP-InP electroabsorption optical modulators with high extinction ratio, low drive voltage, and high modulation bandwidth at λ=1.3 μm are reported. The devices have a tapered-fiber-to-modulator-to-tapered-fiber extinction ratio greater than 20 dB at a drive voltage of <5 V. Very low capacitance modulators (<0.2 pF) were fabricated using SiO₂ bonding pad isolation, resulting in a measured electrical modulation bandwidth in excess of 20 GHz     

Fiber-coupling-operated orthogonal-linear-polarization Nd:YAGmicrochip laser: photothermal beat-frequency stabilization andinterferometric displacement measurement application

The Nd³⁺:YAG microchip laser is operated at orthogonal-linear-polarized two frequencies (λ=1.06 μm). A low crosstalk of 10^-4 is accomplished by means of the fiber-coupled laser diode pumping. The effect of another fiber-coupled laser diode irradiation on the beat frequency is investigated in terms of photothermally induced stress. The beat frequency of typically 100 MHz is stabilized within ±1 MHz by means of the photothermal feedback control of the cavity stress. The utility of the laser in heterodyne interferometric displacement measurement with a good linearity and high resolution is demonstrated     

Dependence of differential quantum efficiency on the confinementstructure in InGaAs/InGaAsP strained-layer multiple quantum-well lasers

An internal efficiency of 91% was obtained with In_0.7Ga _0.3As/InGaAsP strained-layer multiple quantum well (MQW) lasers emitting at a wavelength of 1.5 μm. The dependence of the reciprocal differential quantum efficiency on the length of the laser cavity shows that the absorption loss in the InGaAsP (λ=1.3 μm) confinement layer caused by carrier overflowing into the confinement layer reduces the internal efficiency     

Nonsymmetric Mach-Zehnder interferometers used as low-drive-voltagemodulators

Optical communications systems require fast optical modulators which are compatible with existing microwave-frequency drive circuits and which have low voltage requirements. The authors have designed and demonstrated a novel type of integrated optical modulator: a nonsymmetric Mach-Zehnder interferometer, which has both low switching voltage and efficient coupling to microwave-frequency drive circuits. In 2-cm-long devices, made in z-cut LiNbO₃, switching voltages of 3.2 V and better than 20-dB extinction ratio were measured at λ=1.3 μm. Device performance in the nonsymmetric devices was independent of the asymmetry, which indicates that devices of this kind are tolerant of fabrication variations     

3.5-mm-square InGaAs p-i-n photodiodes and their application tooptical-axis arrangement between 1.3-μm laser diodes and a SMF

InGaAs p-i-n photodiodes (PD) with 3.5-mm×3.5-mm-large photosensitive area have been fabricated using chlorine-vapor-phase-epitaxial (C-VPE) growth. They showed high responsivity of 0.95 A/W (λ=1.3 μm) and 1.2 A/W (λ=1.55 μm) and good homogeneity in the whole area. Long-term reliability was confirmed through high-temperature aging tests at 150°C up to 5200 hours. A PD with two pairs of parallel electrodes (PE-PD) was applied to optical-axis arrangement between 1.3-μm laser diodes (LD's) and a single mode fibre (SMF). The beam position of a LD was detected in error within ±20 μm using PE-PD prior to coupling of a LD beam into a SMF. Total inspection time was reduced to one third the original time     

Coherent frequency-domain reflectometry for characterization ofsingle-mode integrated-optical waveguides

Based on the principles of optical frequency domain reflectometry (OFDR), a highly resolving and sensitive technique suitable for detecting, localizing, and quantifying weakly reflecting irregularities in single-mode optical waveguides is developed. A distributed feedback (DFB)-laser diode at λ₀≅1.3 μm tuned within a range of Δλ≅6 nm and Δv≅1 THz, respectively, is used as a source in the experimental arrangement. An auxiliary interferometer is employed so that the tuning need not be linear in time, in contrast to early implementations. At present, with waveguide structures on InP under test, a spatial resolution of 50 μm and a dynamic range of about 60 dB are obtained. These data surpass OFDR results published so far. Prospects of closing the gap to coherence-domain reflectometric results and specific advantages make OFDR a promising technique     

Continuous operation of high-power (200 mW) strained-layerGa1-xInxAs/GaAs quantum-well lasers with emissionwavelengths 0.87⩽λ⩽0.95 μm

Separate confinement single-quantum-well lasers with 100-120 Å-thick strained Ga_1-xIn_xAs/GaAs active layers have been grown on (100) GaAs substrates by metalorganic chemical vapour deposition. Ten-stripe proton-implanted arrays with 90 μm-wide aperture and 250 μm cavity length emit 200 mW CW optical power at wavelengths 0.87⩽λ⩽0.95 μm. Lifetest data on an uncoated device emitting 90 mW/facet at 50°C and λ=0.95 μm suggest a mean-time-to-failure in excess of 2500 h at room temperature. The performance of lasers with strained Ga_1-xIn_xAs quantum wells is comparable to that of unstrained Al_xGa_1-xAs/GaAs quantum-well lasers without facet coating