研究目的
To measure the nonlinear transmittance of a diffusion-doped single crystal ZnSe:Fe2+ at a wavelength of 2940 nm at low and room temperatures, and to investigate the effects of lasing and non-resonant absorption.
研究成果
The nonlinear transmittance of ZnSe:Fe2+ was successfully measured, showing values around 70% at room temperature and 77% at low temperature under high fluence. Lasing was observed at low temperatures, indicating high gain, and non-resonant absorption was identified, likely from doping-induced crystal imperfections. The experimental data agreed well with theoretical calculations, confirming the model's validity. Future studies should focus on optimizing doping processes to minimize non-resonant losses and further investigate lasing effects.
研究不足
The presence of lasing at low temperatures distorts transmittance measurements, requiring surface matting to reduce its effect. Non-resonant absorption limits maximum transmittance to less than 100%, possibly due to crystal stoichiometry issues from doping. The transverse distribution approximation and neglect of diffraction effects in calculations may introduce errors.
1：Experimental Design and Method Selection:
The experiment used an optical setup similar to previous work, involving a YAG:Er3+ laser to measure transmittance through a ZnSe:Fe2+ sample. The method included nonlinear transmittance measurements with high-power laser pulses, accounting for Gaussian beam distribution and temperature variations.
2：Sample Selection and Data Sources:
A single-crystal ZnSe:Fe2+ sample doped by diffusion on both sides, with a thickness of 1.22 mm and Fe2+-enriched layers of about 100 μm, was used. Data were collected from laser pulses and photodetectors.
3：22 mm and Fe2+-enriched layers of about 100 μm, was used. Data were collected from laser pulses and photodetectors.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment included a YAG:Er3+ laser, photodetectors (PD29 and PD47 types), neutral filters, an optical cryostat, a Tektronix DPO 7254 oscilloscope, and a Shimadzu UV-3101PC spectrometer. Materials included the ZnSe:Fe2+ sample and filters.
4：Experimental Procedures and Operational Workflow:
The sample was placed in a cryostat, and laser pulses at 2940 nm wavelength were directed through it. Transmittance was measured by comparing signals from reference and measuring photodetectors with and without the sample, using a procedure involving signal processing to remove constant and high-frequency components. Measurements were done at room temperature and -168°C, with fluences of 1.3 J cm?2 and 0.4 J cm?
5：3 J cm?2 and 4 J cm?Data Analysis Methods:
2.
5. Data Analysis Methods: Data were analyzed using an oscilloscope for signal recording, and transmittance was calculated as the ratio of signals, accounting for Fresnel reflections. A theoretical model based on rate equations for radiation propagation in a medium with three levels and non-resonant absorption was used for comparison with experimental results.
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