Extremely large differential gain of 1.26 μm GaInNAsSb-SQW ridgelasers

The differential gain of long wavelength GaInNAs-based quantum film (QF) lasers and highly strained GaInAs-based QF lasers have been investigated for the first time. These lasers were grown by gas-source molecular beam epitaxy, and include a small amount of Sb to improve the crystalline quality. GaInNAsSb single quantum well (SQW) ridge lasers that oscillate at 1.258 μm have an extremely large differential gain of 1.06×10^-15 cm² in spite of the SQW lasers; therefore GaInNAsSb lasers are suitable for high-speed lasers in the long wavelength region     

Continuous wave operation of 1.26 μm GaInNAs/GaAsvertical-cavity surface-emitting lasers grown by metalorganic chemicalvapour deposition

Electrically pumped near 1.3 μm GaInNAs/GaAs vertical-cavity surface-emitting lasers grown by metalorganic chemical vapour deposition are demonstrated for the first time. The threshold current and voltage under continuous wave operation of a 10×10 μm² oxide aperture device were 7.6 mA and 2.8 V, respectively. The output power exceeded 0.1 mW and the slope efficiency was ~0.1 W/A     

High reliability low-threshold InGaAsP ridge waveguide lasersemitting at 1.3 μm

The fabrication, performance, and reliability of InP/InGaAsP ridge waveguide lasers emitting at 1.3 μm is described. The structure requires only one stage of planar wafer growth and simple fabrication steps and is therefore an inherently low-cost product. Threshold currents are typically 25-30 mA, and the external quantum efficiency is 20-25% per facet. Output power in the fundamental mode is maintained to above 10 mW, while total power in excess of 100-mW CW at 20° has been obtained. The life test data have been fitted to a power-law drift model to predict long-term behavior and is consistent with total lifetimes in excess of 25 years. The device is eminently suited for applications in high-reliability high-capacity fiber-optic communications systems     

InP microdisk lasers on silicon wafer: CW room temperatureoperation at 1.6 μm

Microdisk lasers are fabricated in an InP:InGaAs MQW heterostructure transferred onto silicon. The CW room temperature laser operation of such devices at 1.6 μm is reported     

Wideband and high-power compressively strained GaInAsP/InPmultiple-quantum-well ridge waveguide lasers emitting at 1.3 μm

Compressively strained 1.3-μm GaInAsP/InP multiple-quantum-well (MQW) ridge waveguide lasers were fabricated. Through optimizing the total well thickness, large bandwidth over 11 GHz was achieved, together with high quantum efficiency of about 0.48 W/A and high power output of 60 mW before rollover. The laser also showed less temperature sensitivity up to an elevated temperature of 85°C     

Low-threshold 1.5 μm compressive-strained multiple- andsingle-quantum-well lasers

Design considerations for low-threshold 1.5-μm lasers using compressive-strained quantum wells are discussed. Parameters include transparency current density, maximum modal gain, bandgap wavelength, and carrier confinement. The optical confinement for a thin quantum well in the separate-confinement heterostructure (SCH) and the step graded-index separate-confinement heterostructure (GRINSCH) are analyzed and compared. 1.5-μm compressive-strained multiple- and single-quantum-well lasers have been fabricated and characterized. As a result of the compressive strain, the threshold current density is loss limited instead of transparency limited. By the use of the step graded-index separate-confinement heterostructure to reduce the waveguide loss, a low threshold current density of 319 A/cm² was measured on compressive-strained single-quantum-well broad-area lasers with a 27 μ oxide stripe width     

High performance 0.1 μm gate-length p-type SiGe MODFET's andMOS-MODFET's

High performance p-type modulation-doped field-effect transistors (MODFET's) and metal-oxide-semiconductor MODFET (MOS-MODFET) with 0.1 μm gate-length have been fabricated on a high hole mobility SiGe-Si heterojunction grown by ultrahigh vacuum chemical vapor deposition. The MODFET devices exhibited an extrinsic transconductance (g_m) of 142 mS/mm, a unity current gain cut-off frequency (f_T) of 45 GHz and a maximum oscillation frequency (f_MAX) of 81 GHz, 5 nm-thick high quality jet-vapor-deposited (JVD) SiO₂ was utilized as gate dielectric for the MOS-MODFET's. The devices exhibited a lower gate leakage current (1 nA/μm at V_gs=6 V) and a wider gate operating voltage swing in comparison to the MODFET's. However, due to the larger gate-to-channel distance and the existence of a parasitic surface channel, MOS-MODFET's demonstrated a smaller peak g _m of 90 mS/mm, f_T of 38 GHz, and f_max of 64 GHz. The threshold voltage shifted from 0.45 V for MODFET's to 1.33 V for MOS-MODFET's. A minimum noise figure (NF_min) of 1.29 dB and an associated power gain (G_a) of 12.8 dB were measured at 2 GHz for MODFET's, while the MOS-MODFET's exhibited a NF _min of 0.92 dB and a G_a of 12 dB at 2 GHz. These DC, RF, and high frequency noise characteristics make SiGe/Si MODFET's and MOS-MODFET's excellent candidates for wireless communications     

InGaAsSb-AlGaAsSb distributed-feedback lasers emitting at 1.72μm

We have developed distributed-feedback ridge waveguide lasers based on AlGa(In)AsSb emitting at 1.72 μm. The distributed feedback is obtained by first-order Cr-Bragg gratings defined on both sides of the laser ridge. The threshold current under pulsed operation at room temperature was around 180 mA and an output power of 1.5 mW was obtained. The gratings lead to a side-mode suppression ratio of 27 dB     

GaInAsSb-AlGaAsSb tapered lasers emitting at 2 μm

Tapered oscillators fabricated from GaInAsSb-AlGaAsSb quantum-well structure are reported for the first time. The quantum-well laser structure, grown by molecular beam epitaxy, has broad-stripe pulsed threshold current densities as low as 330 A/cm² at room temperature. One tapered laser emitting at 2.02 μm has exhibited continuous wave (CW) output power up to 750 mW, with power in the near-diffraction-limited central lobe as high as 200 mW     

Three-stage ultra-high-density multi/demultiplexer coveringlow-loss fibre transmission window 1.26-1.63 μm

An optical multi/demultiplexer with 2010 channels for 10 Gbit/s transmission which covers the whole low-loss fibre wavelength range from 1.26 to 1.63 μm is described. It was achieved using a three-stage tandem configuration that used arrayed-waveguide gratings with Gaussian passbands     

High performance 0.1 μm dynamic threshold MOSFET using indiumchannel implantation

In this letter, we demonstrate a high-performance 0.1 μm dynamic threshold voltage MOSFET (DTMOS) for ultra-low-voltage (i.e., <0.7 V) operations. Devices are realized by using super-steep-retrograde indium-channel profile. The steep indium-implanted-channel DTMOS can achieve a large body-effect-factor and a low V_th simultaneously, which results in an excellent performance for the indium-implanted DTMOS     

High performance damascene metal gate MOSFETs for 0.1 μm regime

A novel transistor formation process (damascene gate process) was developed in order to apply metal gates and high dielectric constant gate insulators to MOSFET fabrication and minimize plasma damage to gate insulators. In this process, the gate insulators and gate electrodes are formed after ion implantation and high temperature annealing (~1000°C) for source/drain formation, and the gate electrodes are fabricated by chemical mechanical polishing (CMP) of gate materials deposited in grooves. Metal gates and high dielectric constant gate insulators are applicable to the MOSFET, since the processing temperature after gate formation can be reduced to as low as 450°C. Furthermore, process-damages on gate insulators are minimized because there is no plasma damage caused by source/drain ion implantation and gate reactive ion etching (RIE). By using this process, fully planarized metal (W/TiN or Al/TiN) gate transistors with SiO₂ or Ta₂O₅ as gate insulators were uniformly fabricated on an 8-in wafer. Further, the damascene metal gate transistors exhibited low gate sheet resistivity, no gate depletion and drastic improvement in gate oxide integrity, resulting in high transistor performance     

Tensile-strained GaInAsP-InP quantum-well lasers emitting at 1.3μm

Tensile-strained GaInAsP-InP quantum-well (QW) lasers emitting at 1.3 μm are investigated. Low-pressure metalorganic chemical vapor deposition (LP-MOCVD) is used for crystal growth. High-resolution X-ray diffraction shows good agreement with theoretical simulation, photoluminescence spectra have good energy separation between light-hole and heavy-hole bands due to biaxial tension. The lowest threshold current density for infinite cavity length J_th/N_w ^∞ of 100 A/cm² is obtained for the device with -1.15% strain and N_w=3. The amount of strain which gives the lowest J_th/N_w^∞ experimentally clarified is around -1.2%. Threshold current of a buried-heterostructure (BH) laser is reduced to be as low as 1.0 mA. Enhanced differential gain of 7.1×10^-16 cm² is also confirmed by measurements of relative intensity noise. Much improved threshold characteristic with the feasibility of submilliamp threshold current can be achievable by optimizing the BH structure. The tensile-strained QW laser emitting at 1.3 μm with very low power consumption is attractive for the light source of fiber in the loop system and optical interconnection applications     

1.5 μm wavelength distributed reflector lasers with verticalgrating

A 1.5 μm wavelength distributed reflector laser, consisting of a distributed Bragg reflector rear facet and a distributed feedback region, was realised using deep-etching technology. A low threshold current of I_th=12.4 mA and a high differential quantum efficiency of η_d=42% from the front facet was achieved with a submode suppression ratio of 33 dB (I=2.4 I_th) for a fifth-order grating, 220 μm long and 6 μm wide device at room temperature     

High-stability 1.5 μm external-cavity semiconductor lasers forphase-lock applications

Applications using phase-locked semiconductor lasers, such as homodyne detection, require lasers with narrow linewidth and high-frequency stability. The design and operating characteristics of two 1.5 μm external-cavity semiconductor lasers built for such applications are described. The measured beat linewidth is 4 kHz, and the spectral density of relative frequency noise deviates significantly from the intrinsic white spectrum only at frequencies below 4 kHz. It is estimated that this frequency jitter will induce approximately 1.1° RMS phase error in a second-order homodyne optical phase-lock loop that is optimized for the present beat linewidth     

Circular beam emission from 1.3 μm InGaAsPstrained-multiquantum-well lasers

The beam divergence in the vertical direction from a graded index separate confinement heterostructure (GRINSCH) multiquantum-well (MQW) laser has been studied. It is demonstrated both theoretically and experimentally that a circular beam MQW laser can be produced by choosing appropriate thicknesses for the GRINSCH layers, while maintaining other desired laser characteristics. The beam divergence is found to be more affected by the index change induced by injected carriers than by strain in the MQW active layer. Theoretical results are in good agreement with the measurements for 1.3-μm InGaAsP strained MQW lasers     

InGaAs-InGaAsP buried heterostructure lasers operating at 2.0 μm

Buried heterostructure lasers with highly strained InGaAs-InGaAsP active regions, emitting at 2 μm have been fabricated and tested. The lasers exhibited threshold current densities of 500 A/cm² for 1-mm-long cavities, an internal loss of 11 cm^-1, and characteristic temperatures as high as 50°C. The gain characteristics were also investigated and a linewidth enhancement factor of 8 was determined     

CW 100 kW radio frequency-free-electron laser design at 10 μm

The authors describe the 100 kW continuous-wave (CW) radio frequency free-electron laser at 10 μm to be built at Boeing Defense and Space Group in collaboration with Los Alamos National Laboratory. The authors discuss the criteria which led to the selection of the operating point. The authors outline the single-accelerator master-oscillator power-amplifier concept. This approach and the wavelength were chosen on the basis of maximum cost-effectiveness, including utilization of existing hardware, reasonable technical risk, and potential for future applications. The major experimental goals for the average power laser experiment (APLE) program are discussed, and the expected performance is considered     

High performance of 1.55-μm buried-heterostructurevertical-cavity surface-emitting lasers

We report a record low threshold current of 1.55-μm vertical-cavity surface-emitting laser (VCSEL). Thin-film wafer-fusion technology enables InP-based buried heterostructure VCSELs to be fabricated on GaAs-AlAs distributed Bragg reflectors. Threshold current density is independent of mesa size, and a 5-μm VCSEL exhibits a threshold current as low as 380 μA at 20°C and a single transverse mode up to the maximum optical output power under continuous-wave operation     

Coherent laser radar at 2 μm using solid-state lasers

The development of a coherent laser radar system using 2-μm Tm and Tm, Ho-doped solid-state lasers, which is useful for the remote range-resolved measurement of atmospheric winds, aerosol backscatter, and differential absorption lidar (DIAL) measurements of atmospheric water vapor and CO₂ concentrations, is described. Measurements made with the 2-μm coherent laser radar system, advances in the laser technology, and atmospheric propagation effects on 2-μm coherent lidar performance are discussed. Results include horizontal atmospheric wind measurements to >20 km. vertical wind measurements to >5 km, near-horizontal cloud returns to 100 km, and hard target (mountainside) returns from 145 km