Application Cases

Experiment Title: All-Electro-Optic Fast Linear Broadband Frequency Modulation Experimental System

Testing Equipment: Voltage Amplifier, Waveform Generator, Oscilloscope, High Voltage Detector, etc.

Experiment Process:

Figure 1: Fast Linear Broadband Frequency Modulation Nd:YVO4 Laser System

The system structure of the fast linear broadband frequency modulation laser is shown in Figure 1. The resonator length is 65mm, and the resonator transmittance is 10%. Under an absorption pump power of 4W, after inserting a standard etalon with a thickness of 0.2mm and a reflectivity of 70%, a single-frequency output of about 0.9W was obtained by adjusting the tilt angle of the etalon. The frequency modulation device composed of an RTP electro-optic etalon (RTPetalon) and an RTP electro-optic frequency modulation crystal (RTPcrystal) was installed into the resonator in the order shown in the figure. The insertion of a high-reflection standard etalon and a high-reflection RTP electro-optic etalon into the resonator introduced significant resonator loss, and the RTP electro-optic frequency modulation crystal also introduced insertion loss, which led to a decrease in laser output power. After optimizing the positions and angles of the intra-cavity elements, a stable single-frequency output of 160mW was achieved.

Figure 2: Single-Frequency Laser Output Monitored by FPI

The application of dual etalons further enhanced the stability of the single-frequency output of the standing-wave resonator. The single-frequency output mode of the laser is shown in Figure 2. The RTP electro-optic etalon and RTP electro-optic frequency modulation crystal utilize the linear electro-optic effect of the electro-optic crystal to achieve fast frequency tuning. They are connected to two voltage amplifiers, respectively. These voltage amplifiers receive the initial voltage signal from the signal generator and can amplify the initial signal from DC to 1kHz by 1000 times, outputting a voltage signal of 0~±5kV.

Figure 3: Voltage Amplifier Amplification Performance Test System

Synchronous frequency modulation requires that the external electric field voltage be applied synchronously to the RTP electro-optic etalon and RTP electro-optic frequency modulation crystal. We first used a high voltage detector to test the synchronous amplification performance of the two high voltage amplifiers, as shown in the test system in Figure 3.

The signal generator is set to a dual-channel synchronous output state, with the two high voltage amplifiers connected to channels 1 and 2 of the arbitrary waveform generator, respectively. The amplifier amplifies the signal voltage by 1000 times and outputs the same voltage at two parallel output ports. One port is directly connected to the RTP crystal, and the other port is connected to the high voltage detector. The high voltage detector reduces the voltage by 1000 times and sends it to a four-channel oscilloscope. The channels 1 and 2 of the signal generator are connected to channels 1 and 2 of the oscilloscope, respectively, and also connected to the input ports of the two high voltage amplifiers. The output signals of the high voltage detector are connected to channels 3 and 4 of the oscilloscope, allowing the oscilloscope to simultaneously observe and record the voltage output status of the four channels.

Experimental Results:

Figure 4: Synchronous scanning voltage of RTP electro-optic etalon (RTPetalon, solid line) and RTP electro-optic frequency modulation crystal (RTPcrystal, dashed line), inset: non-linear voltage change near zero

Figure 4 shows the enlarged data test results of a 200Hz triangular waveform voltage. The synchronous triangular wave voltage applied to the RTP electro-optic etalon and RTP electro-optic frequency modulation crystal has amplitudes of 1300V and 5800V, respectively, with zero voltage offset, meaning the amplitude in the positive and negative directions of the voltage is essentially the same. From the test results, the voltage amplifier can amplify the 200Hz triangular wave signal with nearly ideal amplification performance (amplification performance weakens for repetition frequencies above 200Hz), and the synchronous change state between signals is good.

In the experiment, we applied voltage to the RTP electro-optic etalon and RTP electro-optic frequency modulation crystal in the form of the signal shown in Figure 4, obtaining symmetric triangular waveform fast linear broadband frequency-modulated laser output. Based on this, we will test the bandwidth, linearity, and single-frequency output linewidth of the frequency-modulated laser.

Voltage Amplifier Recommendation: ATA-7050

Figure: Specifications of the ATA-7050 High Voltage Amplifier

This material is compiled and released by Aigtek Antai Electronics. For more case studies and product details, please continue to follow us. Xi'an Aigtek Antai Electronics has become a widely recognized supplier of instruments and equipment with a broad product line and considerable scale in the industry. Sample machines are available for free trial.