An external cavity wavelength-locked red semiconductor laser with a narrow-linewidth was designed and fabricated. The AlGaInP strained quantum wells were meticulously designed and grown,while the epitaxial layer of a high-power red semiconductor laser was synthesized using metal-organic chemical vapor deposition (MOCVD).The chips were fabricated by photolithography, metal electrode fabrication, cavity surface coating and other processes. The prepared laser chip with the cavity length of 1.5 mm has a strip width of 100 μm. The chip was made into a laser device through packaging technique, and an external resonant cavity was constructed using a Volume Bragg Grating. A series of oexperiments were conducted to optimize the performance of laser devices, and the characteristics of spectrum, power and other parameters in the condition of free running spectrum and wavelength-locked spectrum at different temperatures. A narrow-linewidth red semiconductor laser with the central wavelength of 640 nm, the linewidth of 0.11 nm, and the power of 2.7 W was obtained by means of the continuous drive current measurement at room temperature with the drive current of 3 A and fiber parameters of 50/125. In addition, the output power of 5.02 W was achieved with the method of the quasi-continuous drive current of 5 A.The power loss of the external cavity mode-locked using VBG is controlled within 3%.
In this work, based on the double cylindrical wave holographic interference method, a broadband chirped volume Bragg grating (CVBG) in photo-thermo-refractive glass (PTR) has been fabricated and studied, which has a diffraction bandwidth of about 23.8 nm. The transmittance and diffraction efficiency (DE) of the prepared CVBG were measured. The results showed that the DE and refractive index modulation (RIM) of the CVBG samples increased first and then decreased with the increase of the heat treatment time. And the transmittance of all samples decreased, indicating that the losses (sum of absorption and scattering) of the samples increased. It was found that the absorption coefficients of all samples did not exceed 0.1cm-1 even after prolonged heating, and the scattering losses accounted for the main part losses of the CVBG. Then, the thermostatic duration of the sample was shorter during heat treatment at the first time, the starting point of the RIM of CVBG became higher, which is expected to obtain higher RIM and DE of the CVBG in the subsequent heat development process. Although increasing the dose of UV exposure can reduce the losses of the CVBG, it is not conducive to the improvement of the RIM and DE of the CVBG. Therefore, we have made restrictions on both the dose of UV exposure and the duration of heat treatment. Finally, based on the fundamental matrix (F-matrix) method, the influence of the key structural parameters of the CVBG on its diffraction characteristics was analyzed, and a guidance scheme for making high-efficiency CVBG was proposed.
Vortex volume grating (VVG) has advantages of high diffraction efficiency (DE), excellent angular selectivity, broad spectral band, and flexible design, making it a good candidate as an orbital angular momentum (OAM) generator in high power laser system.. In our research, a vortex volume grating with a relative diffraction efficiency of 84.58% and an angular spectrum of 1.864 mrad at 1064 nm is fabricated, and the refractive index modulation (RIM) is retrieved.
In this work, a chirped volume Bragg grating (CVBG) with over 40 nm high efficiency broadband spectra for pulse compression of near 100 fs was studied. Based on the fundamental matrix method, the effects of various structural parameters of CVBG on its diffraction characteristics were analyzed and then a design of broadband and high efficiency CVBG was proposed. Afterward, the monolithic CVBG was utilized to stretch and recompress a 100 fs pulse with a center wavelength of 1030 nm. The result shows this device has a high diffraction efficiency (84%) and a fine reciprocity. For the fabrication of large-size broadband CVBGs, double cylindrical wave holographic interference in photo-thermorefractive (PTR) glass was applied to achieve a wide range uniform and stable light field, which could greatly minimize unnecessary space chirp.
In this paper, we report the optical and thermal properties of a new Nd-doped phosphate laser glass. Glass samples with
0.5-3.7 wt% Nd-doping concentrations were prepared, annealed, cut and polished for different measurements, including
glass density and refractive index, absorption spectra and emission cross section, as well as laser properties. A Mach-
Zehnder interferometer was used to measure the temperature coefficient of refractive index (dn/dT) and optical path
length (dS/dT) in the temperature range of 30-100 °C. Moreover, by increasing the glass temperature up to 500 °C, the
thermal expansion of this new glass was also measured. On the basis of these optical, thermal and thermo-optic
parameters, we calculated and analyzed some of glass parameters, such as the electronic polarizability of oxygen ions,
the optical basicity of this phosphate-based glass, and especially discussed their thermal shock resistance properties. It is
suggested that this new Nd-doped phosphate laser glass is an excellent candidate for high energy and high repetition rate
laser applications.
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