InAs/InP量子点激光器制备工艺研究

报道了通过化学湿刻蚀制备窄脊条InAs/InP量子点激光器的方法。激光器脊条主要是由半导体材料InGaAs和InP构成,通过选择合适配比的H2SO4∶H2O2∶H2O和H3PO4∶HCl腐蚀溶液和InP的腐蚀方向,在室温下选择性地腐蚀了InGaAs和InP,获得了窄脊条宽为6μm的量子点激光器。此激光器能够在室温连续波模式下工作,激射波长在光纤通信重要窗口1.55μm,单面最大输出功率超过12mW。     

Realization of dot DFB lasers

Dot lasers with first-, second- and third-order gain coupled distributed feedback (DFB) gratings have been realized by low damage dry etching in combination with wet chemical etching and epitaxial over-growth. This technique allows above room temperature (RT) operation of dot DFB lasers with dot diameters down to 85 nm. The laser spectra show the expected emission of gain coupled DFB lasers. Threshold current densities between 1.1 kA/cm/sup 2/ and 2.6 kA/cm/sup 2/ could be obtained depending on size of the active region. An improvement in T/sub 0/ could be demonstrated comparing 0-D/1-D/2-D lasers on the same wafer. Based on the dot grating geometry improvement of the side mode suppression ratio (SMSR) was observed for broad-area dot DFB lasers.     

InAs/GaInAs quantum dot DFB lasers emitting at 1.3 μm

Singlemode operation of 1.3 μm InAs/GaInAs quantum dot lasers has been achieved using the concept of complex coupled distributed feedback. Mode selection was realised by laterally patterned metal gratings. At room temperature the lasers show stable singlemode emission with sidemode suppression ratios of up to 55 dB, threshold currents as low as 17 mA and output powers of up to 8 mW under continuous wave operation     

Singlemode emission at 2 μm wavelength with InP based quantum dash DFB lasers

Long wavelength distributed feedback (DFB) laser diodes based on InP quantum dash-in-a-well material have been fabricated and investigated at room temperature under continuous-wave operation. Singlemode emission of InP laser diodes at wavelengths above 2 mum is demonstrated for the first time.     

Aging characteristics of InGaAsP/InP DFB lasers

Aging tests of InGaAsP/InP DFB lasers with a constant light output of 5 mW/facet and ambient temperatures 25°C and 40°C have been carried out. Up to the present, with an aging time of more than 2000 h for six lasers, appreciable degradations have been observed in their driving currents and spectra. This indicates that the corrugation grating near the active region has little influence on short-term reliability of DFB lasers.     

Emission dynamics of dot and wire DFB lasers

Emission dynamics of InGaAs-InGaAsP dot and wire DFB lasers were systematically investigated and compared with quantum-well lasers. Accordingly, the effective carrier capture times, which limit the maximum modulation bandwidth of low-dimensional semiconductor lasers, were determined and compared for these lasers. A quite large effective capture time of about 350 ps was found for the dot laser in contrast to about 56 ps for the quantum-well laser. This is attributed to a dramatically reduced volume of active region which induces a large scaled-up quantum capture time in the dot lasers. The systematic comparison of the quantum-well, -wire and -dot lasers reveal the dominant limitation of geometry effect on the high-speed modulation of quantum-wire and -dot lasers except when the packing density of the dots or wires is increased.     

Vertical-external-cavity surface-emitting lasers and quantum dot lasers

The use of cavity to manipulate photon emission of quantum dots (QDs) has been opening unprecedented opportunities for realizing quantum functional nanophotonic devices and quantum information devices....     

Hybrid LPE/MBE-grown InGaAsP/InP DFB lasers

InGaAsP/InP distributed-feedback (DFB) lasers operating at 1.5 ?m have been successfully fabricated by a hybrid growth technique of liquid phase epitaxy (LPE) and molecular beam epitaxy (MBE). A threshold current of 180 mA at 23°C and single-longitudinal-mode operation have been obtained.     

InAs/InP量子点激光器中欧姆接触合金层特性研究

合金层与InAs/InP量子点激光器的接触电阻对激光 器的性能有很大影响,而接触电阻的 大小与合金材料、退火温度和退火时间有关。本文采用Au/Ni/Au/Ge做InAs/InP量子点激光 器的欧姆接触合金层,通过改变退 火温度和退火时间调节量子点激光器中接触电阻的阻值。实验发现,退火时间对接触电阻的 改变不 大,但是提高退火温度却能极大地降低接触电阻的阻值。实验获得了Au/Ni/Au/Ge 合金层与InAs/InP量子点激光器最佳欧姆接触条件,通过矩阵传输法测得相应接触电阻率为 1.34×10－6 Ω·cm²。在此条件下,制备激射中心波长为 1.577μm的多模量子点 激光器,室温下单面最大输出功率达到和超过39mW。     

Colliding-pulse modelocked quantum dot lasers

Colliding pulse modelocking is demonstrated for the first time in quantum dot lasers. Using 3.9 mm-long devices with a 245 /spl mu/m-long central absorber, 7 ps pulses at a repetition rate of 20 GHz is obtained. For Gaussian pulses a time-bandwidth product close to the Fourier transform limit is determined. These results confirm the potential of quantum dot lasers for high repetition rate harmonic modelocking.     

Relaxation oscillations of quantum dot lasers

The relaxation oscillation frequency of quantum dot lasers is modelled theoretically. Its dependency on the driving current, maximum gain, intersublevel relaxation time and homogeneous broadening is investigated. For suitable, feasible quantum dot laser parameters, relaxation oscillation frequencies up to 10 GHz are predicted. Making these devices useful for 5 Gbit/s communication systems     

Static and dynamic properties of laterally coupled DFB lasers based on InAs/InP QDash structures

Laterally coupled, complex distributed feedback lasers based on AlInGaAs/InAs/InP quantum dash layers were fabricated by maskless focused ion beam lithography. Continuous-wave powers above 30 mW at room temperature, sidemode suppression ratios of 44 dB and a modulation bandwidth of 7.6 GHz were demonstrated.     

Gain-coupled DFB lasers with truncated quantum well second-ordergratings

Static and dynamic properties of in-phase gain-coupled multiple quantum well distributed feedback (DFB) lasers with second-order gratings have been measured at 1.55 μm. Devices with both facets antireflection coated and with a κL product between 4 and 5 have achieved a sidemode suppression ratio of over 63 dB. Relative intensity noise measurements have confirmed that the dynamic properties of second-order truncated well gain-coupled (GC)-DFB lasers are comparable to those with first-order truncated-well gratings     

λ/4-shifted InGaAsP/InP DFB lasers

lambda/4-shifted InGaAsP/InP DFB lasers were studied theoretically and experimentally. The effect of reflectivities at the end of a DFB region and that of alambda/4shift position were analyzed in terms of stability of single-longitudinal-mode operation and asymmetric power distribution. The shift of thelambda/4-shift position from the center to a certain place in the DFB region, with the end reflectivities less than several tenths of a percent, seemed most effective for efficient power extraction and reproducible DSM operation. The devices emitting at 1.5 μm range were fabricated by using negative and positive photoresists and employing one-step holographic exposure. They exhibited single-longitudinal-mode operations just at or closely around the center of the stopband, i.e., the Bragg wavelength. The slight wavelength deviations from the center were found to be attributed to the accidental phase-shift variations from the optimal value. Concerning such deviations in the fabricated devices, a simple and useful criterion, for example,P_{0}/P_{1} geq 2-3atI/I_{th} = 0.9, for stable DSM operation was presented. Statistically, single-longitudinal-mode operations were observed in 95 devices out of 100, and the theoretical prediction was verified. The side-mode-suppression ratios under high-speed direct modulation were 35 dB or more.     

Optically pumped surface-emitting DFB GaInAsP/InP lasers with circular grating

The lasing action in surface-emitting DFB lasers with circular grating (SE-CG DFB) is reported for the first time. 1.283 mu m laser oscillation is demonstrated by optical pumping. The threshold pumping power density is estimated to be 16.2 kW/cm/sup 2/. The pulsed output power is more than 25 mW.<>     

Room-temperature operation of InAs quantum-dash lasers on InP (001)

The first self-assembled InAs quantum dash lasers grown by molecular beam epitaxy on InP (001) substrates are reported. Pulsed room-temperature operation demonstrates wavelengths from 1.60 to 1.66 μm for one-, three-, and five-stack designs, a threshold current density as low as 410 A/cm² for single-stack uncoated lasers, and a distinctly quantum-wire-like dependence of the threshold current on the laser cavity orientation. The maximal modal gains for lasing in the ground-state with the cavity perpendicular to the dash direction are determined to be 15 cm^-1 for single-stack and 22 cm^-1 for five-stack lasers     

Longitudinal-mode behaviour of ?/4-shifted InGaAsP/InP DFB lasers

Longitudinal-mode behaviour of ?/4-shifted InGaAsP/InP DFB lasers fabricated by the nega-posi method have been studied. The deviation of the main mode from the centre of the stopband, which was attributed to an accidental additional phase shift introduced around the ?/4-shifted position, was related to the intensity ratio of the main to side mode below the threshold, and it was much larger compared to conventional DFB lasers for the devices with small deviation. The intensity ratio above the threshold was about 35 dB or more in 100% direct modulation for most of the lasers.     

Design of tunneling injection quantum dot lasers

In recent years, semiconductor quantum dot (QD) lasers have attracted considerable attention due to their potentia applications[1]. Although QD laser has been predicted can have more excellent performance than conventional quan- tum well laser, so far tem…     

Inhomogeneous gain effects in quantum dot lasers

A comparison of optical and electrical derivative spectroscopy on a dual-state lasing InAs/GaAs quantum dot bilayer device is presented. The junction voltage cannot be described by a quasi-Fermi level separation and only partial clamping above the laser threshold was observed, demonstrating inhomogeneous gain. There is also competition between transverse optical modes which must be taken into account for a full understanding of dual-state lasing