Study On Novel Optically-Pumped Vertical-External-Cavity Surface-Emiting Lasers

Optically pumped vertical external cavity surface emitting semiconductor laser is a new type of semiconductor laser which is based on the curruent injected vertical cavity surface emitting lasers and combined with the technology of diode-pumped solid-state laser. It combines both the advantages of them. It can output the circular TEM00 mode Gaussian beam, and output high power high brightness laser, and the frequency doubling or mode-locked components are convenient to insert into the cavity, to achieve efficiently frequency doubling or mode-locking operation, thus the output wavelength can be extended, or the high repetition rate laser pulses and ultrashort laser pulses at the magnitude of femtosecond were obtained. Therefore, this kind of laser is widely applied in the optical clock, optical fiber communications, laser color display and laser biomedical and other fields .The structures of optically pumped vertical external cavity surface emitting semiconductor lasers are very simple. There are two growth structures of the epitaxial wafers, one is the bottom emitting structure,and the other is top emitting structure. There are two optically pumped methods, too. The corresponding wavelength range of semiconductor material system used in vertical external cavity surface emitting laser cover a broad band from the ultraviolet to visible to infrared. The most mature material systems are 800nm-1.5μm band. The refractive index, band gap energy and thermal conductivity, and other related parameters of these common ternary, quaternary alloys need to calculate for the design of the epitaxial wafers.The reflectivity formulas of distributed Bragg reflector were derived using the transfer matrix method,and the reflectivity and reflection bandwidth were investigated at different pairs, different incident and exit medium. The distributed Bragg reflector was designed by using 30 pairs Al0.12gaas / Al0.9gaas, which was alternatively grow atλ/ 4 optical thickness,and the forward and backward incident reflective spectrum were calculated.In the designing, ingaas / algaas / gaas quantum well material system was used, 12 strain multiple quantum wells were used to form the resonant periodic gain structure; the related resonator parameters of vertical external cavity surface emitting laser were calculated and designed.The wafers'substrate was processed by mechanical thinning and chemical etching method, the surface of the wafer after mechanical thinning, rapid corrosion and selective corrosion, was observed under the microscope.DBR reflectivity spectrum was measured,and compared with the calculated theoretical spectrum. An OPS-VECSEL of around 50mm cavity length, 50mm mirror curvature radius, and 99% output mirror reflectivity was setup.At last, the VECSEL's characteristics were measured and detailed analyzed, including the spontaneous emission spectrum, output power spectrum, the output beam spot and the output laser spectrum under different pump powers.