Buried heterostructure InGaAsP/InP strain-compensated multiple quantum well laser with a native-oxidized InAlAs current blocking layer

An InAlAs native oxide is used to replace the p-n reverse-biased junction in a conventional buried heterostructure InP-based laser. This technique reduces the number of regrowth steps and eliminates leakage current under high-temperature operation. The InAlAs native oxide buried heterostructure (NOBH) laser with strain-compensated InGaAsP/InP multiple quantum well active layers has a threshold current of 5.6 mA, a slope efficiency of 0.23 mW/mA, and a linear power up to 22.5 mW with a HR-coated facet. It exhibits single transverse mode with lasing wavelength at 1.532 mu m. A characteristic temperature (T-0) of 50 K is obtained from the NOBH laser with a nonoptimized oxide layer width. (C) 1998 American Institute of Physics. [S0003-6951(98)01352-7].

Design and performance of monolithic integrated electro-absorption modulated distributed feedback laser - art. no. 67820Y

High performance InGaAsP/InGaAsP strained compensated multiple-quantum-well (MQW) electroabsorption modulators (EAM) monolithically integrated with a DFB laser diode have been designed and realized by ultra low metal-organic vapor phase epitaxy (MOVPE) based on a novel butt joint scheme. The optimization thickness of upper SCH layer for DFB and EAM was obtained of the proposed MQW structure of the EAM through numerical simulation and experiment. The device containing 250(mu m) DFB and 170(mu m) EAM shows good material quality and exhibits a threshold current of 17mA, an extinction ratio of higher than 30 dB and a very high modulation efficiency (12dB/V) from 0V to 1V. By adopting a high-mesa ridge waveguide and buried polyimide, the capacitance of the modulator is reduced to about 0.30 pF corresponding to a 3dB bandwidth more than 20GHz.

Impact of diode facet reflectivity on the fiber grating external cavity semiconductor laser

The scattering matrix method is used to analyze the multiple reflection effect between the laser diode facet and the fiber grating facet by considering the fiber grating external cavity laser diode (FGECL) as a four-mirror cavity laser. When neglecting other important parameters such as butt-coupling distance between the diode and the fiber facets, coupling efficiency, external cavity length, it is shown that low reflectivity is not a crucial factor for the laser characteristics such as SMSR. Experimentally high SMSR fiber grating external cavity laser is fabricated with a relatively large residual facet reflectivity (about 1%), which is coincident with our simulation results.

A Selective-Area Metal Bonding InGaAsP-Si Laser

A 1.55-mu m hybrid InGaAsP-Si laser was fabricated by the selective-area metal bonding method. Two Si blocking stripes, each with an excess-metals accommodated space, were used to separate the optical coupling area and the metal bonding areas. In such a structure, the air gap between the InGaAsP structure and Si waveguide has been reduced to be negligible. The laser operates with a threshold current density of 1.7 kA/cm(2) and a slope efficiency of 0.05 W/A under pulsed-wave operation. Room-temperature continuous lasing with a maximum output power of 0.45 mW is realized.

Generation of the high efficiency high peak-power femtosecond blue optical pulse

The analysis and calculation of the compensation for the phase mismatch of the frequency-doubling using the frequency space chirp introduced from prisms are made. The result shows that suitable lens can compensate the phase mismatch in a certain extent resulting from wide femtosecond spectrum when the spectrum is space chirped. By means of this method, the experiment of second harmonic generation is carried out using a home-made femtosecond KLM Ti:sapphire laser and BBO crystal. The conversion efficiency of SHG is 63 %. The average output power of blue light is 320 mW. The central wavelength is 420 nm. The spectrum bandwidth is 5.5 nm. It can sustain the pulse width of 33.6 fs. The tuning range of blue light is 404-420 nm,when the femtosecond Ti:sapphire optical pulse is tuned using the prisms in the cavity.

Experimental study on K alpha X-ray emission from intense femtosecond laser-solid interactions

The characteristics of K alpha X-ray sources generated by p-polarized femtosecond laser-solid interactions are experimentally studied in the relativistic regime. By use of knife-edge image technique and a single-photon-counting X-ray CCD camera, we obtaine the source size, the spectrum and the conversion efficiency of the Ka X-ray sources. The experimental results show that the conversion efficiency of Ka photons reaches an optimum value of 7.08 x 10(-6)/sr at the laser intensity of 1.6 x 10(18) W/cm(2), which is different from the Reich's simulation results (Reich et al., 2000 Phys. Rev. Lett. 84 4846). We find that about 10% of laser energy is converted into the forward hot electrons at the laser intensity of 1.6 x 10(18) W/cm(2).

Room-Temperature Continuous-Wave Operation of InGaN-Based Blue-Violet Laser Diodes with a Lifetime of 15.6 Hours

We report our recent progress of investigations on InGaN-based blue-violet laser diodes (LDs). The room-temperature (RT) cw operation lifetime of LDs has extended to longer than 15.6 h. The LD structure was grown on a c-plane free-standing (FS) GaN substrate by metal organic chemical vapor deposition (MOCVD). The typical threshold current and voltage of LD under RT cw operation are 78 mA and 6.8 V, respectively. The experimental analysis of degradation of LD performances suggests that after aging treatment, the increase of series resistance and threshold current can be mainly attributed to the deterioration of p-type ohmic contact and the decrease of internal quantum efficiency of multiple quantum well (MQW), respectively.

808 nm high-power laser grown by MBE through the control of Be diffusion and use of superlattice

808 nm high-power laser diodes are gown by MBE. In the laser structure, the combination of Si-doped GRIN (graded-index) region adjacent to n-AlGaAs cladding layer with reduced Be doping concentration near the active region has been used to diminish Be diffusion and oxygen incorporation. As compared with the laser structure which has undoped GRIN region and uniform doping concentration for Si and Be, respectively, in the cladding layers, the slope efficiency has increased by about 8%. Typical threshold current density of 300 A/cm(2) and the minimum threshold current density of 220 A/cm(2) for lasers with 500 mu m cavity length are obtained. A high slope efficiency of 1.3 W/A for coated lasers with 1000 mu m cavity length is also demonstrated, Recorded CW output power at room temperature has reached 2.3 W.

HIGH-EFFICIENCY TOP SURFACE-EMITTING LASERS FABRICATED BY 4 IMPLANTATION USING TUNGSTEN WIRE AS MASK

We report the results of a high efficiency room temperature continuous wave (cw) vertical-cavity surface-emitting laser. The structure is obtained by four deep H+ implantation using tungsten wires as the mask. The fabrication process is the simplest ever reported in vertical-cavity surface-emitting laser fabrication. The largest differential quantum efficiency of 65% and maximum cw light output power over 4 mW have been achieved for the 15X15 mu m(2) device. (C) 1995 American Institute of Physics.

Efficient Mode-locked and Q-switched Nd∶YVO_4 Laser with Semiconductor Saturable Absorber Mirror

We reported an efficient diode pumped Nd ! YVO, 1 064 nm laser passively mode-locked and Q-switched by a semiconductor saturable absorber mirror(SESAM). At the incident pump power of 7. 5 W, 2. 81 W average output power was obtained during stable CW mode locking with a repetition rate of 111 MHz. The optical conversion efficiency was 37. 5% , and the slope efficiency was 39%. So far as we know, this is the highest optical-optical conversion efficiency with a SESAM at home.

High-Power Distributed Feedback Laser Diodes Emitting at 820nm

By etching a second-order grating directly into the Al-free optical waveguide region of a ridgewaveguide（RW） AlGaInAs/AlGaAs distributed feedback（DFB） laser diode,a front facet output power of 30mW is obtained at about 820nm with a single longitudinal mode. The Al-free grating surface permits the re-growth of a high-quality cladding layer that yields excellent device performance. The threshold current of these laser diodes is 57mA,and the slope efficiency is about 0.32mW/mA.

Temperature Distribution in Ridge Structure InGaN Laser Diodes and Its Influence on Device Characteristics

Time-dependent thermal simulation of ridge-geometry InGaN laser diodes is carried out with a two-dimensional model. A high temperature in the waveguide layer and a large temperature step between the regions under and outside the ridge are generated due to the poor thermal conductivity of the sapphire substrate and the large threshold current and voltage. The temperature step is thought to have a strong influence on the characteristics of the laser diodes. Time-resolved measurements of light-current curves,spectra, and the far-field pattern of the InGaN laser diodes under pulsed operation are performed. The results show that the thermal lensing effect improves the confinement of the higher order modes and leads to a lower threshold current and a higher slope efficiency of the device while the high temperature in the active layer results in a drastic decrease in the slope efficiency.

1.3-μm uncooled 10 Gb/s directly modulated MQW AlGaInAs/InP laser diodes

In this paper, we report a novel 1.3-μm uncooled AlGaInAs/InP multiple quantum well (MQW) ridge waveguide laser diodes. By optimizing the design of MQW structure and facet coatings, together with the application of reversed-mesa ridge waveguide (RM-RWG) structure, polyimide planarization, and lift-off processes technology, an uncooled 1.3-μm, 10-Gb/s directly modulated MQW ridge waveguide laser diode was successfully fabricated. The threshold current and the slope efficiency were 7 mA and 0.48 mW/mA, respectively. The directly modulated bandwidths of 11 and 9.2 GHz were achieved at room temperature and 80 Celsius degrees, respectively.

5.3-W Nd:YVO_4 passively mode-locked laser by a novel semiconductor saturable absorber mirror

We report a diode end-pumped continuous wave (CW) passively mode-locked Nd:YVO4 laser with a homemade semiconductor saturable absorber mirror (SESAM). The maximum average output power is 5.3 W at the incident pump power of 17 W, which corresponds to an optical-optical conversion efficiency of 31.2% and slope efficiency of 34.7%. The corresponding optical spectrum has a 0.2-nm full width at half maximum (FWHM), and the pulse repetition rate is 83 MHz.

A Wavelength Tunable DBR Laser Integrated with an Electro Absorption Modulator by a Combined Method of SAG and QWI

We report a wavelength tunable electro-absorption modulated DBR laser based on a combined method of SAG and QWI. The threshold current is 37mA and the output power at 100mA gain current is 3.5mW. When coupled to a single-mode fiber with a coupling efficiency of 15% ,more than a 20dB extinction ratio is observed over the change of EAM bias from 0 to -2V. The 4.4nm continuous wavelength tuning range covers 6 channels on a 100GHz grid for WDM telecommunications.