Cui Bifeng

Characteristics of high power LEDs at high and low temperature

The high power light emitting diodes (LEDs) based on InGaN and AlGaInP individually are tested on line at temperatures from −30 to 100 °C. The data are fitted to measure the relationship between temperature and the properties of forward voltage, relative light intensity, wavelength, and spectral bandwidth of two different kinds of LEDs. Why these properties changed and how these changes reflected on applications are also analyzed and compared with each other. The results show that temperature has a great influence on the performance and application of power LEDs. For applications at low temperature, the forward voltage rising and the peak wavelength blue-shifting must be considered; and at high temperature, the relative light intensity decreasing and the peak wavelength red-shifting must be considered.

A tunnel regenerated coupled multi-active-region large optical cavity laser with a high quality beam

A novel coupled multi-active-region large optical cavity structure cascaded by a tunnel junction is proposed to solve the problems of facet catastrophic optical damage (COD) and the large vertical divergence caused by the thin emitting area in conventional laser diodes. For a laser with three active regions, a slope efficiency as high as 1.49 W/A, a vertical divergence angle of 17.4°, and a threshold current density of 271 A/cm2 are achieved. By optimizing the structural parameters, the beam quality is greatly improved, and the level of the COD power increases by more than two times compared with that of the conventional laser.

A Novel Kind of Transverse Micro-Stack High-Power Diode Bars

Novel transverse micro-stack semiconductor laser bars are put forward to improve the output optical power of semiconductor laser bars at low injection current. More importantly, the novel laser bars have a coupled large optical cavity, which can overcome the problem of catastrophic optical damage and improve light beam quality due to the coherently coupled emitting along the transverse direction. The micro-stack tunnel regeneration tri-active region laser structure was grown by metal organic chemical vapour deposition. For a weakly coupled uncoated device, the optical power exceeds 60W under 50A driving current and the slope efficiency reaches 1.55W/A. Further experiments show that the perpendicular divergence of 23° is achieved from transverse strongly coupled devices.

Multi-active region laser diode with a narrow beam divergence angle

A novel large optical cavity laser diode, which consists of multi-active regions cascaded together through tunnel junctions, is proposed. After growing the epi-layers with LP-MOCVD system on GaAs substrate, the ridge waveguide laser structure is fabricated, and it shows a transverse divergence angle as low as 14.4°.

Cascaded coupled large optical cavity semiconductor lasers

Novel multi-active region semiconductor lasers with large coupled optical cavity and high quantum efficiency has been proposed and fabricated. The external and differential quantum efficiency are 2.9 and 3.0 W/A, and the output light power is /spl sim/5W when the injecting current equals 2A for the four active region 980 nm strained InGaAs/GaAs QW lasers. The fundamental mode light output with perpendicular angle /spl les/17/spl deg/ for this type of large coupled optical cavity laser has been achieved.