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     

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     

Tunable absolute-frequency laser at 1.5 μm

Frequency stabilisation of a two-frequency diode-pumped Er,Yb:glass laser is demonstrated using Doppler-broadened or saturated-absorption lines of ¹³C₂H₂. Continuous tunability in the 1530-1550 nm range is obtained. Beat note measurements lead to a frequency accuracy better than 10 kHz for a 10s response time     

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     

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     

Reliability of InAlGaAs strained-quantum-well lasers operating at0.81 μm

Preliminary reliability studies of strained In_0.15Al _0.13Ga_0.72As quantum-well lasers operating at 0.81 μm are reported. InAlGaAs lasers, a possible replacement for AlGaAs lasers, have been studied with respect to three failure mechanisms. Uncoated In_0.15Al_0.13Ga_0.72As quantum-well lasers have exhibited catastrophic optical damage limits of 1.87 MW/cm², which is equal to that of similar AlGaAs lasers. Further, the lasers are both free of <100> DLD-induced sudden failures and exhibit low degradation rates even in this early stage of their development     

Low-threshold-current-density 1.5 μm lasers using compressivelystrained InGaAsP quantum wells

A low-threshold current density (J_th) of 140 A/cm² for broad-area 1.5-μm semiconductor lasers with uncoated facets is demonstrated at a cavity length of 3.5 mm. This was achieved by the use of a single InGaAsP quantum well (QW) of 1.8% compressive strain inside a step-graded InGaAsP waveguide region. Low-cavity losses of 3.5 cm^-1 and a relatively wide quantum well as compared to InGaAs wells of equivalent strain contribute to this high performance. Double QW devices of 2 mm length showed threshold current densities of 241 A/cm². Quaternary single and double QWs of similar width but only 0. 9% strain gave slightly higher threshold current density values, but allowed growth of a 4 QW structure with a J_th of 324 A/cm² at L=1.5 mm     

Novel design of AlGaInAs-InP lasers operating at 1.3 μm

A novel design of AlGaInAs-InP lasers operating at 1.3 μm is proposed. A distinctive attribute of the proposed design is that the AlInGaAs active region is surrounded by an AlInAs electron stopper layer on the p-side and an InP hole stopper layer on the n-side. The stopper layers do not impede the carrier injection into the active region and at the same time reduce the thermionic emission of carriers out of the active region. Utilization of stopper layers allows one to increase the value of internal quantum efficiency and to select the waveguide material corresponding to the optimum optical confinement factor value     

Lasing at 2·08 μm and 1·38 μm in a holmiumdoped fluoro-zirconate fibre laser

The authors report for the first time a fibre laser operating beyond the 1·55 μm communications window. Using a holmium doped fluoro-zirconate fibre, laser emission occurs from the three-level 2·08 μm transition, and also at 1·38 μm via a cascading transition     

15 W diode-side-pumped Tm:YAG waveguide laser at 2 μm

The high-power side-pumped operation of a double-clad Tm:YAG waveguide laser at 2.02 μm, using two proximity-coupled 20 W diode pump lasers, is reported. A slope efficiency of 43% was observed with respect to incident diode power, giving a maximum output power of 15 W. The double-clad geometry ensures diffraction-limited output in the guided plane     

High power semiconductor laser injection-locking at 1.3 μm

The injection-locking properties of a high power antireflection coated 1.3-μm slave laser subjected to relatively low injection powers from a distributed feedback (DFB) laser and from a tunable external cavity laser have been investigated. Narrow linewidth operation (~40 kHz) was demonstrated and the tuning range within two slave modes (~10 GHz) and over the gain profile (~40 nm) was investigated. In addition, the tracking properties of the slave laser for both frequency and phase modulated injected light was evaluated at 1 Gb/s, in which the fidelity was judged from bit-error-rate measurements. The maximum locked power under 1 Gb/s frequency modulation was about 145 mW, limited by the available master power; approximately 300 μW was injected into the slave     

Dark-line-resistant, aluminum-free diode laser at 0.8 μm

Quantum-well, lattice-matched InGaAsP lasers emitting at 0.8 μm are shown to exhibit resistance to 〈100〉 dark-line growth. This property in conjunction with the aluminum-free device structure augurs well for future high-power diodes and arrays operating near this wavelength     

High-power highly strained InGaAs quantum-well lasers operating at1.2 μm

High-power highly strained In_xGa_1-xAs quantum-well lasers operating at 1.2 μm are demonstrated. The edge emitting broad area (BA) laser diode structures are grown by metal organic vapor phase epitaxy at low growth temperatures using trimethylgallium, trimethylindium, and arsine sources. In the laser structure, an InGaAs QW is sandwiched between the GaAs waveguide and AlGaAs cladding layers. The operating wavelength for the laser diode at room temperature (20°C) is about 1206 nm, which redshifts to 1219 nm at 46°C. The transparency current density for the BA laser diodes is as low as 52 A/cm² and the characteristic temperature value is 76 K. High-power laser operation in the pulse mode (about 1.6 W) at room temperature was achieved     

Tunable laser-diode-pumped Nd:YAG microcrystal lasers at 1.4 μm

TEM₀₀ laser operation of a monolithic Nd:YAG crystal laser has been achieved on three transitions at 1.414 μm, 1.444 μm and at 1.431 μm with laser diode pumping at 808 nm. The laser threshold was 1.5 W and the maximum output power 50 mW. The gain linewidths at 1.414 μm and 1.444 μm were determined by means of temperature tuning the microcrystal lasers. Calculations for designing tunable single frequency microcrystal lasers have been performed     

Frequency stabilization of laser diodes at 0.83 μm using a fiberoptic coupler

Frequency stabilization of a fiber pigtailed laser diode discriminator is reported. The fiber coupler acts as a nearly-balanced-arm Michelson interferometer. The peak transmission signal is used for feedback control of the injection current of the laser diode. Because the sensing port can be isolated from the signal transmission port, the package design is very simple and can be implemented in an all-fiber fashion. The frequency fluctuation of a 0.83-μm test laser stabilized by this method is less than ±4 MHz. This scheme is applicable to longer-wavelength (1.2-1.6 μm) laser diodes; the stabilized lasers can be packaged easily     

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     

1.3 μm fluoride fibre laser

Laser action has been achieved in the 1.33-1.34 μm range using an Nd³⁺-doped fluorozirconate glass multimode fibre. These operating wavelengths are the closest to the important telecommunications channel at 1.3 μm of any reported for a glass laser     

Antiguided laser array structure at 1.48 μm fabricated withoutovergrowth

The authors describe the fabrication of five-element antiguided laser arrays at 1.48 μm using a novel material design which removes the need for overgrowth. Adding undoped passive waveguiding layers to the standard laser design significantly alters the shape of the far field emission from the lasers, showing that the array elements are pulled in phase with each other     

GaInAsN/GaAs laser diodes operating at 1.52 μm

GaInAsN/GaAs double quantum well (DQW) lasers have been grown by solid source molecular beam epitaxy (MBE). Room-temperature pulsed operation is demonstrated for a ridge waveguide laser diode at a wavelength of 1517 nm. This is the first report of room-temperature laser emission in the 1.5 μm range based on GaAs     

High-power, high-temperature operation of GaInAsSb-AlGaAsSbridge-waveguide lasers emitting at 1.9 μm

Ridge-waveguide lasers emitting at ~1.9 μm have been fabricated from a multiple-quantum-well heterostructure with an active region consisting of five GaInAsSb wells and six AlGaAsSb barriers. At room temperature, single-ended cw output power as high as 100 mW has been obtained. The maximum cw operating temperature is 130°C, with a characteristic temperature of 85 K between 20 and 80°C