1.3 μm multiquantum well decoupled confinement heterostructure(MQW-DCH) laser diodes

A 1.3-μm multi-quantum-well decoupled confinement heterostructure (MQW-DCH) laser diode has been developed. This structure introduces internal barriers between the active quantum wells and the optical waveguide. It is thus possible to have, at the same time, deep quantum wells to prevent carrier leakage and a strong optical waveguide with a high confinement factor. The barrier parameters have been optimized using numerical modeling tools, and the DCH laser diode has been built using chemical beam epitaxy. The broad-area transparency current density is 140 A-cm^-2, the internal efficiency is 0.83, the waveguide loss is 5 cm^-1. and T₀ = 62 K. Ridge waveguide laser diodes have a room temperature threshold of 8 mA and an efficiency of 0.32 mW/mA     

一种新型超高速多量子阱半导体激光器

报道了一种主要用作超高速光纤通信光时分复用(OTDM)系统的新型光源,即10GHz的被动外腔式锁模多量子阱半导体激光器,其具有脉冲宽度为2.9ps,波长调谐范围为1.53～1.57μm(40nm),输出光波长可精确稳定在1.55μm,锁模光脉冲的重复频率为10GHz,平均输出光功率为1mW及较小的时间抖动性(<0.6ps)等优点。     

Low-threshold dye laser pumped by visible laser diodes

The author describes a continuous-wave (CW) dye laser has been pumped by laser diodes for the first time. Two 10-mW visible laser diodes were polarization-combined to pump a rhodamine 700 dye jet laser. The absorbed pump threshold power was 5.6 mW, and 0.28 mW of output power was produced at 758 nm. The resonator was scalable and generated over 360 mW with a slope efficiency of 57% when pumped with a DCM dye laser at 660 nm     

Thermal behavior of visible AlGaInP-GaInP ridge laser diodes

The thermal behavior of visible AlGaInP-GaInP ridge laser diodes was investigated numerically and experimentally. It is shown that various parameters critically influence the thermal resistance, R , of such devices. R is inversely proportional to the thermal conductivity of the heat sink. A substantial improvement in R is achieved for junction-side-down mounting compared to junction-side-up. R depends strongly on the width, w, of the ridge, and this effect is different for junction-side-up or junction-side-down mounting. In the first case, R~log(w) and in the second, R~1/w. The thickness of the soldering material is a sensitive parameter which may increase the value of R by up to 15 K/W. For junction-side-up mounted devices, the top metallization layer has a very favorable effect: a 1-μm-thick gold layer reduces R by 30%. It is shown that when a laser is switched on, the thermal steady state is reached in the millisecond time range. The experimental results show very good agreement with numerical data     

Be-implanted GaInAsP/InP double heterojunction laser diodes

Beryllium ion implantation has been used to fabricate broad-area GaInAsP/InP laser diodes operating at a wavelength of 1.3 μm, which have threshold current densities comparable to those obtained using conventional Zn doping during the epitaxial growth process. Both a Be-implant schedule which results in minimal diffusion of the implanted Be and one which results in significant diffusion have been investigated. On most wafers, the average normalized threshold current density (J_{nom} = J_{th}/d) using either implant schedule has been typically 6-8 kA/cm². μm. The lowest Jnomobserved was 4.2 kA/cm². μm and was measured on a "nondiffused" implanted laser.     

Gain mechanism in an (AlGa)As double heterostructure laser

Presented here is substantial evidence of a specific quantum mechanical model for gain in a (AlGa)As double heterostructure laser with a pure active layer. Close quantitative agreement between predicted and measured values substantiates a new model that evolves directly from Stern's theory. A novel method employing picosecond optical probe pulses coupled axially to the semiconductor laser gain guide allows the first direct measurements of guide gain. The concept of optical impulse response is introduced. Current spreading and facet reflectivity are directly measured. The first self-consistent set of characteristic parameters for a specific laser are determined.     

Interband tunneling in heterostructure tunnel diodes

A particular type of tunnel diode, incorporating a wideband tunnel barrier, is studied. Simple analytic expressions are developed for estimating the tunneling coefficients to guide and optimize the design of heterostructure interband tunnel devices. The interband tunneling in such heterostructure tunnel diodes is modeled by a two-band Schrodinger equation. For a certain family of InGaAs/InA/GaAs p-n junction tunnel diodes, the interband transmission coefficients are calculated. The estimated peak currents are shown to compare very favorably with experimental results     

High power, 8.5 W CW, visible laser diodes

Visible laser diodes have been fabricated from AlGaInP operating at approximately 680 nm to high output powers. Broad area lasers with 100 mu m wide emitting apertures operate to greater than 1 W CW with a different efficiency of 38%. The threshold current densities of the material have been measured to be as low as 350 A/cm/sup 2/ for lasers with 30% mirror reflectivities. Monolithic bars 8 mm long with 50 mu m emitting apertures periodically spaced on 500 mu m centres have been fabricated which operate to 8.5 W CW.<>     

Cr:LiCaAlF6 laser pumped by visible laser diodes

A Cr:LiCaAlF₆ laser was pumped using visible lase diodes. Two commercial 10-mW laser diodes were polarization combined to demonstrate lasing in a low-loss resonator. In addition, a higher power 665-nm laser diode was used to pump the laser, producing 15.9 mW CW and 51.8 mW pulsed at 10 Hz. Optical characterization of the gain medium was performed using a dye laser. Gain, loss, slope efficiency, and the dependence of the threshold power on pump wavelength are reported     

InGaN／AlGaN双异质结构蓝光LED的电学和光学性质

研究了ＩｎＧａＮ／ＡｌＧａＮ双异质结构（ＤＨ）蓝光发光二极管（ＬＥＤ）的电学和光学性质，实验表明，器件正向偏压下的Ｉ－Ｖ特性偏离了ｐｎ结二极管的肖克莱模型的结果，并且载流子的主要输运机制与载流子隧穿有关。通过对电致发光（ＥＬ）谱的测量，得到位于２．８ｅＶ的发射峰和位于３．２ｅＶ弱发射峰，随着电流增大而均出现蓝移。对大脉冲电流下ＬＥＤ的特性的退化作了研究。     

Room-temperature operation of MBE-grown InGaP/InGaAlP MQW visible laser diodes

Room-temperature pulsed operation has been achieved, for the first time, in InGaP/InGaAlP multiquantum-well (MQW) laser diodes grown by molecular beam epitaxy (MBE). This MQW laser is composed of 10 nm-thick InGaP well layers and 5 nm-thick InGaAlP barrier layers. The lasing wavelength was 658 nm. The threshold current density and T0 value were 7.6 kA/cm2 and 115 K, respectively.     

Frequency noise reduction of visible InGaAlP laser diodes bydifferent optical feedback methods

The emission spectra of several commercial InGaAlP laser diodes operating in the visible range were investigated. Strong relaxation sidebands at frequency spacings up to 2 GHz were observed in the field spectra. By using optical feedback from an external high-finesse resonator, the laser line-width was reduced from a few hundred megahertz to less than one megahertz. However, only a small part of the laser power was found within the narrow bandwidth, whereas most of the power finds itself in relaxation sidebands a few gigahertz apart from the carrier. The frequency noise reduction was investigated by using an external cavity configuration. With a short cavity length the relaxation oscillation sidebands were completely suppressed, and the laser linewidth was reduced to a few megahertz. Additional strong reduction in the laser linewidth to roughly 50 kHz was obtained using a combination of the external cavity laser with optical feedback from an external high-finesse resonator     

Photoluminescence investigation of the carrier confining propertiesof multiquantum barriers

A comparative luminescence study of two Ga_0.52In_0.48P-(Al_0.5Ga_0.5) _0.52In_0.48P single-quantum-well (SQW) samples with bulk and multiquantum barrier (MQB) barriers is presented. When excess carriers are only created in the quantum wells (QW's) of the samples by resonant excitation using a dye laser, the luminescence efficiency of both samples as a function of temperature is found to be essentially identical. We find, therefore, no evidence for any enhancement in the confining potential of the MQB sample over the bulk barrier sample. From Arrhenius plots of the integrated luminescence intensity, it is found that carrier loss from the QW is dominated by a nonradiative loss mechanism with an activation energy considerably smaller than that expected from direct thermal loss of electrons and holes into the barriers. We suggest that the improved device characteristics reported for lasers containing MQB's is due to effects other than the quantum interference of electrons     

Continuous wave visible InGaP/InGaAlP quantum well surface emitting laser diodes

Vertical cavity top surface emitting lasers in the 0.66 mu m visible spectral region were fabricated by the metal-organic chemical vapour deposition technique. The continuous wave threshold currents I/sub th/ are 3.9 and 4.6 mA at -75 and -25 degrees C, respectively, for 15 mu m diameter devices. The lasers can also be operated at room temperature, but only in a pulsed mode with an I/sub th/ of 12 mA at 25 degrees C.<>     

Lasing mode and spectral linewidth control by phase tunable distributed feedback laser diodes with double channel planar buried heterostructure (DFB-DC-PBH LD's)

Lasing mode selection between ±1 modes across the stop-band and spectral linewidth tunability have been experimentally observed with newly developed phase tunable distributed feedback laser diodes with double channel planar buried hetetostructure (DFB-DC-PBH LD's) for the first time.     

Interstripe coupling and current spreading in a subthreshold double heterostructure twin stripe laser

TWin stripe laser structures show great promise in integrated optics Systems. It has been proposed that optical interactions in such Structures should produce properties such as beam steering, optical pulse generation and bistability. However, fundamental properties of these devices, including the effect of the resistive p-type cladding layer on the current density distribution injected into the active region, the terminal behavior of the device, and the effect of the stripe width and spacing current density distributions have not yet been considered. This paper considers the current density distribution problem of a twin stripe laser, and examines the effect on the distribution of current injection into both stripes, interstripe coupling via the resistance of the p-type cladding layer and the geometric factors of cladding layer thickness, electrode width and spacing. A diode model is assumed for the heterostructure, and finite difference techniques are used to calculate the 2 D potential distribution in the p-type cladding layer and the current density distribution in the active layer. Numerical and experimental results highlight the effect of the nonlinear diode boundary on the current density distribution and show the changes in the current distribution which occur for relatively small fluctuations in current injected into the stripes and equally small changes in the geometry.     

GaInP/AlGaInP index waveguide-type visible laser diodes with dry-etched mesa stripes

GaInP/AlGaInP index waveguide-type visible-light laser diodes with dry-etched mesa stripes have been fabricated by Cl/sub 2/ reactive ion beam etching for the first time. The AlGaInP cladding layer, which is normally very difficult to dry etch due to problems with Al oxidation and the low volatility of In and its reaction products, was etched smoothly with high depth accuracy. The etched mesa stripes were buried by metal organic vapour-phase epitaxy without crystal discontinuity at the regrown surface. The threshold current under room-temperature pulsed operation is 35 mA (L=300 mu m), which is almost the same value as that for wet-etched lasers.<>