Application Cases

Experiment Title: Dye Laser Structure, Wavelength Tuning, and Mode Monitoring

Testing Purpose:Tunable continuous-wave dye lasers currently cover a wavelength range from 365 to 1000 nm. Through frequency-doubling and mixing techniques using nonlinear crystals, the wavelength can be extended to 260 nm. The laser output power can reach above 100 mW (mainly in the red to yellow wavelength range), with a linewidth in the MHz range. The gain medium of the laser, i.e., the laser dye, has reached over 500 varieties, with dozens of commonly used ones. In summary, dye lasers have advantages such as wide tunability, high output power, and the ability to produce continuous wave, Q-switched, and ultrashort pulse outputs. These lasers are widely used in laser spectroscopy, laser biology, laser medicine, and spectral detection of atmospheric environments.

Testing Equipment:High Voltage Amplifier, Signal Generator, Oscilloscope, PZT, Laser Detector, etc.

Experiment Process:

Figure 1: Experimental setup for laser mode monitoring. Two spherical mirrors with low reflectivity form a confocal cavity. By scanning the cavity length of the Fabry-Perot (F-P) cavity using a sawtooth wave output from the high voltage amplifier applied to the PZT on the cavity mirror, the laser output mode and frequency tuning can be monitored. PD, photodetector; Osc, oscilloscope.

According to the setup diagram, the experimental system is constructed using two spherical mirrors to form an F-P cavity for monitoring the output laser mode. The finesse of the monitoring cavity is not required to be high, so ordinary dielectric film mirrors can be used as cavity mirrors. Figure 1 illustrates the mode monitoring part of the dye laser. The sawtooth wave output from the high voltage amplifier is sent to the PZT on the cavity mirror, which can scan the cavity length of the F-P cavity to monitor the laser output mode and frequency tuning.

In the experiment, we used a wavemeter to measure the frequency of the dye laser. The wavemeter has a measurement range of 350-1100 nm and an accuracy of ±0.002 nm (at 1000 nm). The input light to the wavemeter is fiber-coupled, with an incident light power above 20 μW but not exceeding 10 mW.

Experimental Results:

By adjusting the birefringent filter, the laser wavelength can be preliminarily tuned to the desired wavelength. When the birefringent filter is rotated, the position of its transmission peak changes, causing the output laser to mode-hop with a frequency jump range of one thin etalon free spectral range, i.e., 345 GHz (0.41 nm). Rotation of the birefringent filter causes the largest wavelength jump in the laser. When the thin etalon is rotated, its transmission peak position also changes, causing the output laser to mode-hop with a frequency jump range of one thick etalon free spectral range, i.e., 30 GHz (0.036 nm). Both the birefringent filter and the thin etalon can tune the laser frequency. Although the tuning is not continuous, the tuning range is relatively large.

High Voltage Amplifier Recommendation: ATA-7030

Figure: Specifications of the ATA-7030 High Voltage Amplifier

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