Abstract
Femtosecond laser-excited generation of frequency-tunable microwave pulses, based on an unbalanced single-arm interferometer with frequency-to-time mapping, has been proposed and demonstrated with easy-to-obtain commercial devices. The optical wave-to-microwave frequency conversion, which involves continuous tuning in the range from 2.0 GHz to 19.7 GHz, was achieved based on simple spatial–optical group delay adjustment. Additionally, the pulse duration of the microwave waveform was measured to be 24 ns as the length of the linear dispersion optical fiber was fixed at 20 km. In addition, owing to the designs of the single-arm optical path and polarization-independent interference, the generated microwave pulse train had better stability in terms of frequency and electrical amplitude. Furthermore, a near-triangular-shaped microwave pulse at 4.5 GHz was experimentally obtained by the superposition of two generated sinusoidal signals, which verified the potential of this system to synthesize special microwave waveform pulses.
Highlights
Pulsed microwave waveform generation has attracted widespread interest in the past decade due to its important potential applications, including radars, radio-frequency communications, electronic test systems, etc., [1,2,3]
Optical spectral shaping and frequency-to-time mapping technology based on femtosecond laser is regarded as the most effective way to generate pulsed microwave signals without using any reference microwave sources
We proposed and experimentally demonstrated a femtosecond laserexcited frequency-tunable pulsed microwave waveform generator, based on an unbalanced single-arm interferometer with frequency-to-time mapping, which consisted of easy-toobtain commercial devices
Summary
Pulsed microwave waveform generation has attracted widespread interest in the past decade due to its important potential applications, including radars, radio-frequency communications, electronic test systems, etc., [1,2,3]. Optical spectral shaping and frequency-to-time mapping technology based on femtosecond laser is regarded as the most effective way to generate pulsed microwave signals without using any reference microwave sources. Two approaches based on spatial light modulation and optical fiber shapers, respectively, have been proposed to achieve optical spectral shaping. The spatial light modulation method based on a liquid-crystal modulator array can provide frequency tuning in real time, but has a bulky and complicated optical system in free space [16].
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