Beam Properties And Beam Combining Technique For Semiconductor Lasers

Semiconductor lasers have become irreplaceable components of many modern optoelectronic and photonic systems. Study on the radiation properties of semiconductor lasers is desirable to evaluate the coupling efficiency during the optical design. The radiation properties are determined by the structures of semiconductor lasers. Therefore, the waveguide optical modes in the semiconductor lasers with different waveguide structures are investigated by means of optical waveguide theory.With the development of fabrication and packaging techniques, the dimensions of optoelectronic and photonic systems have become smaller and smaller. The far-field radiation models are no longer suitable for the near-field distribution of semiconductor lasers. Moreover, semiconductor lasers are also used as near-field optical virtual probes in near-field high-density optical data storage, nano-lithography, near-field optical imaging and spectral detection etc. Therefore, the near-field characteristics of semiconductor lasers are investigated and the 1-D near-field model for semiconductor lasers is built by using a plane wave spectrum approach.The beam quality factor M2 is now widely used to characterize the quality of laser radiation. The comprehensive analysis and accurate calculations for the beam quality factors of the semiconductor lasers with different waveguide structures are provided based on the non-paraxial second-moment theory. An experimental approach is given for the measurement of the beam quality factors of an InGaAs/AlGaAs SCH DQW laser. It has been shown that the M2 values of semiconductor lasers, which are defined by the second moments, are always larger than unity.The collimating microlens for semconductor lasers are designed and the simulated results are provided. A new wavelength beam combining technique for a high-power laser diode bar by using a temperature gradient heat sink is proposed. The thermal controlling principle of the temperature gradient heat sink is discussed. It is proved by experiment that the linear temperature distribution, which generates linear wavelength spread of the output beams from a LD bar, can be obtained by introducing a temperature gradient heat sink and the output beams can be focused into a relative small spot by using the Czerny-Turner beam combining system.