High-speed modulation of InGaAs-GaAs strained-layer multiple-quantum-well lasers fabricated by chemically assisted ion-beam etching

Graded-index separate-confinement heterostructure (GRINSCH) strained-layer lasers with five In/sub 0.3/Ga/sub 0.7/As quantum wells have been fabricated with cavity lengths from 50 to 400 mu m using chemically assisted ion-beam etching (CAIBE) to form the laser mirrors. The dry-etching process is thermally assisted, which gives a reproducible etching rate. A minimum threshold-current value is observed at a cavity length of 50 mu m, showing that the multiquantum-well design is optimum for short-cavity lasers. A relaxation oscillation frequency of 10 GHz and a -3 dB bandwidth of 15 GHz have been measured on a 200*10 mu m mesa-structure device.<>     

High-speed modulation of 850 nm InGaAsP/InGaP strain-compensated VCSELs

High performance 850 nm InGaAsP/InGaP strain-compensated vertical cavity surface emitting lasers (VCSELs) are demonstrated with superior output characteristics and modulation bandwidths up to 12.5 Gbit/s from 25 to 85/spl deg/C.     

High-speed modulation of semiconductor lasers

An overview is given of the direct modulation performance of high-speed semiconductor lasers. The high-speed response characteristics are described using a cascaded two-port model of the laser. This model separates the electrical parasitics from the intrinsic laser and enables these subsections to be considered separately. The presentation concentrates on the small-signal intensity modulation and frequency modulation responses, and the large-signal switching transients and chirping. Device-dependent limitations on high-speed performance are explored and circuit modeling techniques are briefly reviewed.     

High-speed modulation of semiconductor lasers

An overview is given of the direct modulation performance of high-speed semiconductor lasers, The high-speed response characteristics are described using a cascaded two-port model of the laser. This model separates the electrical parasitics from the intrinsic laser and enables these subsections to be considered separately. The presentation concentrates on the small-signal intensity modulation and frequency modulation responses, and the large-signal switching transients and chirping. Device-dependent limitations on high-speed performance are explored and circuit modeling techniques are briefly reviewed.     

High-speed modulation of vertical-cavity surface-emitting lasers

The IM (intensity modulation) and FM (frequency modulation) characteristics of vertical-cavity surface-emitting lasers are studied. The laser has high FM efficiency and broad IM bandwidth (near 8 GHz) at a very low bias (4.5 mA). Five Gb/s pseudorandom direct intensity modulation of this laser with open eyes is demonstrated.<>     

High-speed performance of partly gain-coupled 1.55-μmstrained-layer multiple-quantum-well DFB lasers

A partly-gain-coupled 1.55-μm distributed feedback (DFB) laser with a strained-layer multiple-quantum-well (MQW) active region with high relaxation oscillation frequency and maximum intrinsic bandwidth of 28 GHz is reported. An effective differential gain of 1.80×10^-15 cm² was achieved, which may be attributed to the strain effect in the MQW active region as well as the combination of the longitudinal gain/index coupling mechanism and fast lateral carrier injection from the cladding layers into the wells     

High-speed multiple-quantum-well optical power amplifier

A multiple-quantum-well optical amplifier is used at 8 Gb/s with high input power such that the average gain is compressed by 2.6 dB. Under these conditions, the output signal level is 35 mW and there is negligible intersymbol interference (ISI) penalty at the receiver. This is possible because of a rapid (7 ps) gain recovery process in the amplifier. A conventional semiconductor amplifier operating at a similar level of gain compression shows 2 dB ISI penalty     

High-speed modulation characteristics of helium-implantedzinc-diffused vertical cavity surface emitting lasers

The high-speed modulation characteristics of helium-implanted zinc-diffused vertical cavity surface emitting semiconductor lasers are measured. Devices with a nominal active region diameter of 10 and 20 μm exhibit a move-out rate of 4.5-6.5 GHz/mW^1/2 and a K factor of 0.65-0.85 ns. Maximum modulation frequency is limited by ohmic heating to approximately 5.5 GHz for 10-μm diameter lasers and to 2.7 GHz for 20-μm diameter lasers. A rolloff in the response below the relaxation oscillation frequency is observed and is explained well by a diffusion capacitance model     

High-speed InGaAsP/InP multiple-quantum-well laser

The authors describe practical high-speed InGaAsP/InP lasers based on compressively strained quantum wells. Buried heterostructure lasers with threshold currents of 10 mA and slope efficiencies of 0.23 mW/mA are used. A modulation bandwidth of 20 GHz is obtained at a low drive current of 90 mA. A K factor of 0.25 ns is obtained and the intrinsic bandwidth of these lasers is estimated at 35 GHz     

High-speed coupled-cavity injection grating lasers with tailored modulation transfer functions

The modulation transfer function can be changed from broad-band to high frequency narrow-band by using a coupled cavity injection grating laser design. Higher order photon-photon resonances are utilized to tailor the modulation function well beyond the relaxation frequency.     

High-speed modulation of 850-nm intracavity contacted shallowimplant-apertured vertical-cavity surface-emitting lasers

GaAs-AlGaAs quantum-well (850 nn) vertical-cavity surface-emitting lasers, with lateral current injection and shallow implanted apertures, show small signal modulation bandwidths of at least 11 GHz and large signal data rates of at least 10 Gb/s. The devices achieved a maximum output power of 2.1 mW, with a threshold current and voltage of 1 mA and 1.71 V, respectively. The shallow implantation step provides photolithographically precise aperture formation (using O⁺ ions), for efficient lateral current injection into the quantum-well active region of the laser, from intracavity contacts. The device aperture was 7 μm in diameter, and the opening in the annular top contact was 13 μm in diameter. The optical spectrum showed several transverse modes     

High-speed large-signal digital modulation of three-terminallow-threshold strained InGaAs/GaAs lasers

We present large-signal digital modulation of very low-threshold strained InGaAs/GaAs single quantum well (SQW) lasers with monolithically integrated intracavity modulators. The voltage controlled intracavity modulator was driven from a simple emitter-follower using a single NPN transistor. Modulation response mas obtained from dc to 1 Gbit/s with a modulation efficiency of 27% and modulation depth of nearly 100%. A bit-error-rate (BER) lower than 10^-11 was measured at 1 Gbit/s with an input signal swing of only 110 mV. We demonstrate the suitability of these devices for ultrabroad-band optical interconnection applications     

Pure strain effects in strained-layer multiple-quantum-well lasers

Pure effects of strain in strained-layer multiple-quantum-well (MQW) lasers are measured separately from quantum effects using Fabry-Perot (FP) lasers with the same well thicknesses but different strains. The differential gain and gain saturation coefficients and the K factors of the lasers are determined by measuring relative-intensity-noise (RIN) spectra with various bias conditions. The differential gain coefficient increases when the compressive strain increases. The gain saturation coefficient also increases with increasing compressive strain. The K factor increases slightly when the compressive strain increases because of the slight increase in the ratio of the gain saturation coefficient to the differential gain coefficient     

Tapered waveguide InGaAs/InGaAsP multiple-quantum-well lasers

The use of ultrathin etch-stop techniques to expand the vertical optical mode size adiabatically in 1.5-μm InGaAs/InGaAsP MQW lasers using a tapered-core passive intracavity waveguide structure is discussed. 30% differential quantum efficiency out the tapered facet, far-field FWHM of ~12° and a butt-coupling efficiency into a cleaved fiber of -4.2 dB, with -1-dB alignment tolerances of ~±3 μm, were achieved     

InAs/InGaAs数字合金应变补偿量子阱激光器

采用气态源分子束外延在InP衬底上生长InAs/InGaAs数字合金应变补偿量子阱激光器.有源区的多量子阱结构由压应变的InAs/In_(0.53)Ga_(0.47)As数字合金三角形势阱和张应变的In_(0.43)Ga_(0.57)As势垒构成.X射线衍射测试表明赝晶生长的量子阱结构具有很高的晶格质量.在100K、130mA连续波工作模式下,激光器的峰值波长达到1.94μm,对应的阈值电流密度为2.58 kA/cm~2.随着温度升高,激光器的激射光谱出现独特的蓝移现象,这是由于激光器结构中相对较高的内部吸收和弱的光学限制引起最大增益函数斜率降低所导致的.     

Tunable multiple-quantum-well distributed-Bragg-reflector lasers as tunable narrowband receivers

Reports a tunable receiver based on a MQW-DBR laser biased just below threshold. The device simultaneously integrates the functions of a tunable filter, optical amplifier, photodetector and, if desired, an FSK discrimination. Using identical devices for both a transmitter and a receiver, we demonstrate FSK transmission up to 250 Mbit/s with sensitivities in the approximately -30 dBm range for 10/sup -9/ BER. Speed is limited by the transmitter FM response, and independent speed measurements indicate a detection bandwidth of at least 1.7 GHz.<>     

High-speed intensity modulation of 1.5 μm DBR lasers withwavelength tuning

Intensity modulation characteristics of a 1.5-μm butt-jointed DBR (distributed-Bragg-reflector) laser with wavelength tuning were studied. A 3-dB modulation bandwidth of 9 GHz and a high relaxation oscillation frequency of more than 10 GHz were obtained for the DBR laser. These characteristics were not affected by changing the lasing wavelength. The chirping width of the DBR laser is lower than that of the distributed feedback (DFB) laser. A clear eye opening and low chirping characteristics were obtained under 5-Gb/s nonreturn to zero (NRZ) pseudorandom modulation with a sufficient extinction ratio     

Self-phase modulation coefficient of multiple-quantum-well optical amplifiers

The self-phase modulation coefficient /spl gamma/ of 1310 nm multiple-quantum-well (MQW) semiconductor optical amplifiers has been investigated. It is found to vary from 16/spl times/10/sup 4/ W/sup -1/ m/sup -1/ for low driving conditions to 3/spl times/10/sup 4/ W/sup -1/ m/sup -1/ for high-driving conditions. This implies that the amount of self-phase modulation occurring in the amplifier is between 1.5-10/spl times/ more than that occurring in the optical fiber following the amplifier. The additional self-phase modulation caused by the semiconductor optical amplifier may be used to achieve compensation for fiber dispersion in optical communication systems at significantly lower average power levels. The linewidth enhancement factor /spl alpha//sub H/ was found to increase from a value of 2 at low driving conditions, in agreement with results reported for MQW lasers, to a value of 3 at high-driving conditions.     

CW high-power single-mode operation of gain-guided stripe-geometry multiple-quantum-well lasers

Stripe-geometry multiple-quantum-well GaAs-GaAlAs lasers grown by MO-CVD are reported to operate fundamental spatial and longitudinal mode up to more than 40 mW CW.     

Mutual injection-locking properties of monolithically-integratedsurface-emitting multiple-quantum-well distributed feedback lasers

The mutual injection-locking properties of a coupled pair of multiple-quantum-well distributed-feedback lasers with grating output couplers were investigated experimentally and theoretically. When the mutual injection locking occurred, the output of one laser decreased while that of the other increased. The locking curve was asymmetric, and a stable and an unstable locking region existed. From the theoretical analysis, it was found that the phase delay with which the electric field emitted from each laser to the other laser significantly influences the locking characteristics. The increase and decrease of the locked output power are caused by the phase delay. It is also shown that the laser which receives the larger optical injection behaves like a slave laser and the laser which has less optical injection behaves like a master laser, and the shape of the locking curve is determined by the balance between the α parameter and the thermal resistance