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)     

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     

InGaAsP/InP separated multiclad layer stripe geometry lasers emitting at 1.5 ?m

InGaAsP/InP separated multiclad layer stripe geometry lasers emitting at 1.5 ?m are reported. The CW threshold current at 25°C is only 82 mA and the maximum temperature where CW lasing is obtained is 65°C. The characteristic temperature of the pulsed threshold current is 60 K. The transverse mode is fundamental and the longitudinal mode is single up to 1.5 times the threshold under CW operation. A few samples operated for over 1000 h at 50°C under constant optical power operation of 5 mW/facet.     

Narrow spectral linewidth 1.5 μm GaInAsP/InP distributed Braggreflector (DBR) lasers

The spectral linewidth of distributed Bragg reflector (DBR) lasers is discussed. The narrowest linewidth of 3.2 MHz was obtained at P =1.5 mW. It was found that narrow spectral linewidths can be obtained constantly for the DBR lasers with long and low optical loss corrugation regions, and with a small coupling coefficient. These results are explained by the external cavity model, which is used in the theoretical analysis. To increase the output power of the narrow-linewidth DBR lasers, AR (antireflection) coating was applied to the output facet. Improved quantum efficiency and submode suppression were achieved. Degradation of the linewidths by the AR coating was insignificant     

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.     

InGaAsP/InP separated multiclad layer stripe geometry laser emitting at 1.5 µm wavelength

We have developed an InGaAsP/InP separated multiclad layer (SML) stripe geometry laser emitting at 1.5 μm wavelength. In this laser, the optical confinement is done by the effective refractive index step owing to the formation of the coupled waveguide outside the stripe region. The current confinement is done by the p-n-p-n structure outside the stripe region. The CW threshold current at 25 °C is only 82 mA for the stripe width and the cavity length of 6 μm and 250 μm, respectively. The maximum temperature where the CW lasing is obtained is 65°C. The characteristic temperature of the threshold current is 60 K. The transverse mode is fundamental up to 1.8 times the threshold. Ten samples are operated at 50°C with constant optical output of 5 mW/facet. These samples are still operating at over 10 000 h with a slight increase in the driving current. The appreciable change in the characteristics due to aging is not observed.     

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     

1.3μm InGaAsP/InP双异质结发光二极管的研究

随着光纤通信系统的发展,长波(1.1—1.7μm)光源的研究巳广泛引起重视。因为在这一波长范围内,石英光纤具有低的传输损耗和材料色散。文献[1]指出,用InGaAsP/InP发光二极管(λ=1.3μm)作光源的系统的传输容量比目前常见的用GaAlAs/GaAs发光     

High-speed operation of 1.5 μm GaInAsP/InP optoelectronicintegrated laser drivers

A 1.5 μm-wavelength high-speed self-aligned constricted-mesa laser diode and an InP MESFET have been integrated monolithically without deterioration in the performance of either device, by using a gate projection process. A broad 3 dB bandwidth of 6.6 GHz was demonstrated for the first time     

Narrow-band vertically stacked filters in InGaAlAs/InP at 1.5 μm

A narrow-band wavelength filter in InGaAlAs/InP has been modeled, fabricated, and tested. A highly asymmetrical, vertically coupled directional coupler operating near the band-edge is formed by a narrow ridge and a wide strip-loaded waveguide. The results of numerical simulation, performed by employing the spectral index method, effective-index method, and a modified coupled-mode theory, are used to fabricate a filter structure with a prescribed filter response. Operation at a center wavelength around 1.5 μm with a bandwidth of 18 Å and transfer efficiency of ~46-68% is achieved. Excellent agreement between the. Designed and measured bandwidth is demonstrated. A multichannel filter device based on an array of individual filters that is capable of extending the usable spectral range is analyzed     

1.55 μm InGaAsP/InP laser buried in a high-resistivity epitaxiallayer on a semi-insulating InP substrate

A buried heterostructure (BH) 1.55 μm laser embedded in a high resistivity epitaxial layer on a semi-insulating substrate is described. This device has a planar surface and both a p- and an n-type electrode on the same side, facilitating integration of electronic devices. Its threshold current is typically 9 mA. Its small signal 3 dB modulation bandwidth was 14 GHz due to the reduction of device resistance and capacitance. No degradation was observed in an aging test at 50°C even after more than 3000 h     

AlGaInAs/InP 1.5 μm MQW DFB laser diodes exceeding 20 GHzbandwidth

Buried mushroom multiquantum well DFB laser diodes with compressively strained GaInAs quantum wells and asymmetric confinement layer design are fabricated with a combined MBE/MOCVD technology. Packaged devices exhibit high -3 dB IM bandwidths for very low bias levels and a record bandwidth for this material system of 21 GHz     

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.     

1.5 μm InP/GaInAsP linear laser array with twelve individuallyaddressable elements

Linear arrays of twelve individually addressable InP/GaInAsP channelled-substrate buried-heterostructure lasers emitting at λ=1.5 μm were fabricated. Spacing between active elements (250 μm) was made to match the fibre spacing in a 12-fibre ribbon. Individual arrays were epoxy bonded, p-side up to metallised BeO carriers. Best case uniformity of laser characteristics within an array is indicated by tight distributions of lasing threshold (9.8±0.9 mA at 30°C) and output powers of (8.6±0.4 mW at 100 mA). While no significant optical crosstalk could be detected, small increases (≃10%) in device lasing thresholds were observed when two adjacent elements were operated CW simultaneously, probably due to the thermal impedance of the epoxy-bond employed and the resultant heating of operating nearest-neighbour devices. Such arrays offer the potential for reduced fibre alignment time per element thus reducing packaging costs per source. In addition, reduced space requirement per source is realised     

Effect of mirror facets on lasing characteristics of distributed feedback InGaAsP/InP laser diodes at 1.5 µm range

The effect of mirror facets on lasing properties of distributed feedback (DFB) InGaAsP/InP laser diodes was studied theoretically and experimentally. A DFB laser with a window region was found to be suitable to examine the effect of mirror facets. The effective reflectivity of a window structure was calculated to be very small, typically as small as 0.03 percent for a few tens of micrometers of the window region. These small effective reflectivities were experimentally confirmed. Three kinds of DFB lasers, i.e., a double-window (DW), a single-window (SW), and a Fabry-Perot (FP), were discussed. Two modes with a separation corresponding to a so-called stopband appeared in a DW-DFB laser, in which almost no reflection at both ends was estimated. On the other hand, the threshold and the resonant wavelength of an SW- and an FP-DFB laser were found to be sensitive to the phases of corrugation at the facets. It turned out, however, that the mirror facet contributed to the single-mode operation due to an asymmetric resonant spectrum and to the reduction in the threshold. Although a low-threshold-current FP-DFB laser was experimentally obtained, the coincidence between the gain peak and the Bragg wavelengths was essential in this type. The SW-DFB laser seemed the most promising among the three types in terms of the stability of the single-mode operation.     

Effect of conduction-band discontinuity on lasing characteristicsof 1.5 μm InGaAs/In(Ga)AlAs MQW-FP lasers

The characteristic temperature (T₀), relaxation frequency (f_r), differential gain (dg /dn) and nonlinear gain coefficient (ϵ) of 1.5-μm InGaAs/In(Ga)AlAs multiple-quantum-well (MQW) Fabry-Perot (FP) lasers grown by gas source molecular beam epitaxy (GSMBE) are reported. It is found that T₀ is little affected by the difference in the conduction band discontinuity. A maximum T₀ value of 86 K is obtained. The dg/dn and ϵ∈ were calculated from the slope of the f_r versus √ power plot and the damping K-factor. It is demonstrated that dg/dn and ϵ of InGaAs/In(Ga)AlAs MQW lasers increase with an increase in the conduction band discontinuity     

Tuning characteristics of optical amplification in 1.5 ?m InGaAsP/InP lasers

The bias current dependence of tuning wavelength in an optical amplifier is investigated in detail. Tuning wavelength decreases below threshold at the rate of ?0.36 ?/mA, mainly due to the change of carrier density, and increases at the rate of 0.11 A/mA above threshold due to the thermal effect.     

High-power 2.0 μm InGaAsP laser diodes

Data detailing the performance of strained-layer InGaAs/InGaAsP double-quantum-well laser diodes operating at 2.0 μm are presented. The total external efficiency and maximum power achieved are 55% and 1.6-W continuous wave (CW), respectively, from a 200-μm gain-guided laser diode. Measurements on gain-guided broad area devices yield an internal efficiency of 0.73 with a distributed loss coefficient, α, of 7.5 cm^-1. The measured threshold current density is 300 A/cm² for a 2-mm-long broad area device operated CW at 25°C     

A GaInAsP/InP tapered-waveguide semiconductor laser amplifierintegrated with a 1.5 μm distributed feedback laser

A GaInAsP/InP index-guided type tapered-waveguide traveling-wave semiconductor laser amplifier (TTW-SLA) with exponential taper structure was realized for the first time and its integration with a 1.5 μm wavelength phase adjusted DFB laser was demonstrated. A reasonable amount of the single-pass gain, which was limited by the residual reflectivity at the output end of the amplifier region, was obtained with no serious problem with the lasing spectrum. A narrow beam divergence of FWHM=5.5° and stable longitudinal mode operation were obtained with the output waveguide width of 20 μm by adopting both a window structure and 7° angled facets. This value agrees well with the theoretically calculated one and proves that single transverse-mode propagation can be attained by an exponentially tapered TTW-SLA with a very wide output end