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Register a new userBroadband Optical Serrodyne Frequency Shifting
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We demonstrate serrodyne frequency shifting of light from 200 MHz to 1.2 GHz with an efficiency of better than 60 percent. The frequency shift is imparted by an electro-optic phase modulator driven by a high-frequency, high-fidelity sawtooth waveform that is passively generated by a commercially available Non-Linear Transmission Line (NLTL). We also implement a push-pull configuration using two serrodyne-driven phase modulators allowing for continuous tuning between -1.6 GHz and +1.6 GHz. Compared to competing technologies, this technique is simple and robust, and offers the largest available tuning range in this frequency band.
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We report the relative frequency stabilization of a distributed feedback erbium-doped fiber laser on an optical cavity by serrodyne frequency shifting. A correction bandwidth of 2.3 MHz and a dynamic range of 220 MHz are achieved, which leads to a strong robustness against large disturbances up to high frequencies. We demonstrate that serrodyne frequency shifting reaches a higher correction bandwidth and lower relative frequency noise level compared to a standard acousto-optical modulator based scheme. Our results allow to consider promising applications in the absolute frequency stabilization of lasers on optical cavities.
A simplified Doppler frequency shift measurement approach based on Serrodyne optical frequency translation is reported. A sawtooth wave with an appropriate amplitude is sent to one phase modulation arm of a Mach-Zehnder modulator in conjunction with the transmitted signal to implement the Serrodyne optical frequency transition, as well as the optical phase modulation of the transmitted signal on the frequency-shifted optical carrier. The echo signal is applied to the other phase modulation arm of the Mach-Zehnder modulator. The optical signals from the two arms are combined in the Mach-Zehnder modulator, whose lower optical sidebands are selected by an optical bandpass filter and then detected in a photodetector. By simply measuring the frequency of the output low-frequency signal, the value and direction of DFS can be determined simultaneously. An experiment is performed. DFS from -100 to 100 kHz is measured for microwave signals from 6 to 17 GHz with a measurement error of less than 0.03 Hz and a measurement stability of 0.015 Hz in 30 minutes when a 500-kHz sawtooth wave is used as the reference.
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