Highly reliable operation of strain-compensated 0.98 μmInGaAs/lnGaP/GaAs lasers with InGaAsP strained barriers for EDFAs

Highly reliable operation of 0.98 μm strain-compensated InGaAs/ InGaAsP lasers is demonstrated for the first time with an estimated lifetime of 170 kh at 25°C. Moreover, we reveal that the degradation rates at 90°C and 80 mW output power are four times smaller than those of identical lasers with GaAs barriers     

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     

Laterally coupled InGaAsP/InP distributed feedback lasers at 1.5μm for chemical sensing applications

Data is presented on stable, tunable single-mode operation from laterally coupled InGaAsP/InP ridge waveguide distributed feedback lasers at ~1.5 μm, suitable for chemical sensing, realised by a greatly simplified fabrication process requiring a single MOCVD growth step. Completed lasers show sidemode suppression ratios as high as 47 dB and wavelength shifts with injection current of 0.035 nm/mA (or 4.5 GHz/mA)     

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     

Continuously tunable 1.5 μm multiple-quantum-well GaInAs/GaInAsPdistributed-Bragg-reflector lasers

The authors demonstrate improved performance in tunable distributed-Bragg-reflector lasers using GaInAs/GaInAsP multiple-quantum-well active layers. They observe linewidths as low as 1.9 MHz, differential quantum efficiencies as large as 33%/front facet at 1.5 μm, and rapid electronic access to all frequencies throughout a 1000 GHz range     

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     

1.5 µm range InGaAsP/InP distributed feedback lasers

Lasing characteristics of InGaAsP/InP distributed feedback (DFB) lasers in the 1.5 μm range were studied theoretically and experimentally. Wave propagation in five-layer DFB waveguides were analyzed to estimate the effect of the structural parameters on threshold conditions. A brief consideration on designing a low threshold laser and its lasing wavelength was made. DFB buried heterostructure lasers with fundamental grating emitting at 1.53 μm were prepared by liquid phase epitaxial techniques. CW operation was confirmed in the temperature rangeof -20° to 58°C, and a CW threshold current was as low as 50 mA at room temperature. A stable single longitudinal mode operation was observed both in dc condition and in modulated condition by a pseudorandom pulse current at 500 Mbits/s. No significant increase in the threshold current was observed after 1400 h continuous CW operation at 20°C.     

Tuning ranges for 1.5 μm wavelength tunable DBR lasers

Tuning ranges for 1.5 μm wavelength tunable distributed Bragg reflector (DBR) lasers were studied experimentally. Over 10.0 nm (1.25 THz) quasicontinuous tuning under 5 mW light output conditions and 4.4 nm (550 GHz) continuous tuning at 1 mW were achieved     

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     

High reflectivity Te-doped GaAsSb/AlAsSb Bragg mirror for 1.5 μmsurface emitting lasers

A high reflectivity GaAsSb/AlAsSb Bragg mirror lattice matched to InP is reported. Operation at 1.5 μm is obtained owing to a large Burstein-Moss shift of GaAsSb absorption caused by a strong N-doping up to 10¹⁹ cm^-2. Peak reflectivity up to 94% has been measured with only 11.5 periods     

1.5-µm λ/4-shifted InGaAsP/InP DFB lasers

A single wavelength light source in 1.5-μm range was developed using InGaAsP/InPlambda/4-shifted distributed feedback (DFB) semiconductor heterostructures. Superiority of thelambda/4-shifted DFB structure in terms of stability of the main mode at the Bragg wavelength was shown theoretically, in which the threshold, the output, and the polarization characteristics were taken into account. Alambda/4-shifted corrugated grating was made by a newly developed negative and positive photoresists technique. Buried heterostructure (BH) diode lasers with nonreflective window ends were fabricated and highly stable single-mode operation with a low threshold was obtained reproducibly. Direct modulation properties and life-tests results indicated that thelambda/4-shifted DFB lasers could be a reliable single-mode light source in a long span lightwave transmission system in 1.5-μm range.     

Strained layer (1.5 μm) InP/InGaAsP lasing opto-electronicswitch (LOES)

We present for the first time a lasing opto-electronic switch (LOES) fabricated in the InP/InGaAsP system. In this device the active region is composed of four 63 Å compressively strained quantum wells. A lasing threshold of 104 mA, or 6933 A/cm², has been observed at a temperature of 298 K, with an external differential quantum efficiency of 14%. The lasing wavelength is centered at 1.52 μm. The current-voltage characteristics manifest pronounced differential negative resistance, characterized by switching and holding voltages of 6.8 V and 1.6 V, respectively, and a switching current density of 33 A/cm². The OFF and ON state resistances are approximately 150 kΩ and 4 Ω, respectively     

High-performance 1.5 μm wavelength InGaAs-InGaAsP strainedquantum well lasers and amplifiers

Improved performance of 1.5-μm wavelength lasers and laser amplifiers using strained In_xGa_1-xAs-InGaAsP quantum well devices is reported. The device structures fabricated to study the effects of strained quantum wells on their performance are described. These devices showed TM mode gain, demonstrating the strain-induced heavy-hole-light hole reversal in the valence band. Lasers using these tensile strained quantum wells show higher and narrower gain spectra and laser amplifiers have a higher differential gain compared to compressively strained quantum well devices. Consequently, the tensile strained quantum well lasers show the smallest linewidth enhancement factor α=1.5 (compression α=2.5) and the lowest K-factor of 0.22 ns (compression K=0.58 ns), resulting in an estimated intrinsic 3 dB modulation bandwidth of 40 GHz (compression 15 GHz)     

InGaAs/GaAs 0.98 μm semi-insulating blocked planar buriedheterostructure lasers employing InGaAsP cladding layers

MOVPE-grown InGaAs/GaAs strained-layered lasers emitting at 0.98 μm have been fabricated using InGaAsP as an alternative to AlGaAs in the cladding layers. Semi-insulating blocked planar buried heterostructure lasers 2.5 μm wide have thresholds as low as 8 mA for 350 μm long devices. With the addition of reflective coatings, slope efficiencies of 0.67 mW/mA and output powers of 60 mW at 160 mA have been obtained     

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     

1.5 μm GaInAsP/InP distributed reflector (DR) lasers with SCHstructure

The large differential quantum efficiency η_df with one-directional output operation obtained in 1.5-μm distributed reflector (DR) lasers using a thin active layer of 50 nm and the separate-confinement heterostructure (SCH) structure is discussed. η _df of the DR laser was experimentally determined to be twice that of distributed-feedback (DFB) lasers cleaved from the same wafer, which indicates high efficiency and high power characteristics of DR lasers     

Intensity cross-correlation functions of the longitudinal modes ofFabry-Perot 1.3 μm InGaAsP lasers

Experimental measurement of intensity cross-correlation functions and autocorrelation functions of the longitudinal nodes of multimode 1.3-μm InGaAsP lasers are discussed. It was found that cross-correlation functions have much more structure than anticipated. As the time delay is increased, the mode interaction can change from correlation to anticorrelation and vice versa. This observation should have a bearing on mode-partition interactions     

Reduced turn-on delay time in 1.3 μm InGaAsP/lnP n-typemodulation-doped strained multiquantum well lasers

Reductions in carrier lifetime, threshold current, and thus turn-on delay time, due to n-type modulation doping, have been experimentally demonstrated in 1.3 μm InGaAsP strained multiquantum well lasers for the first time     

High-speed 1.5 μm self-aligned constricted mesa lasers grownentirely by MOCVD

A self-aligning (SA) process technique to fabricate constricted mesa (CM) lasers is proposed. The controllability of GaInAsP active region volume and InP lateral confining layer widths were greatly improved. Lasers grown entirely by metalorganic chemical vapour deposition (MOCVD) showed very small variation in threshold currents ( I_th=15.2±1.1 mA) and in stray junction capacitances (C=1.62±0.08 pF). A record bandwidth of 10 GHz in the 1.5 μm-wavelength region was demonstrated