Abstract
We proposed a new type of distributed feedback laser with alternating active- and passive-cavities (APC DFB), which enjoys the same quantum well layer where the butt-joint re-growth process can be avoided. By utilizing the chirp characteristics of the APC DFB laser in a delayed self-heterodyne system, a chirped microwave signal with a sweep range up to 40 GHz and a sweep period of 25 μs is generated. The power fluctuation of the generated signal between 0-40 GHz within 30 minutes does not exceed 3 dB, and the scanning range fluctuates about 600 MHz. And experiment results show that the thermal efficiency of the current is always related to the working environment. In the static wavelength measurement, it is controlled by the injection current; when the chirped signal is generated, it is determined by the bias current. In particular, the waveform and the period as well as the sweep range of the generated chirped microwave signals can be accurately tuned by adjusting the modulating current, which has provided a deeper insight into the photonic generation of microwave signals.
Highlights
C HIRPED microwave signals find important applications in modern radar systems [1], wireless communication [2], medical imaging systems [3], and optoelectronic devices [4]
The bandwidth and pulse duration of a chirped microwave signal generated by a sinusoidal wave can reach 40 GHz and 25 μs, respectively, which corresponds to a time bandwidth product of 1×106
A simple and effective method for the generation of chirped microwave signals based on APC DFB laser was proposed and experimentally demonstrated
Summary
C HIRPED microwave signals find important applications in modern radar systems [1], wireless communication [2], medical imaging systems [3], and optoelectronic devices [4]. An early scheme of the microwave photonic methods was based on a five-stage DBR laser, which was adopted to directly modulate the phase region to obtain a microwave sweep source with a sweep range of 38.45 GHz and a sweep period of 5 μs [7]. In [9], a microwave signals up to 40 GHz was generated by two lasers, but this method is time-consuming for frequency matching and very sensitive to the external environment. The Fabry-Perot laser adopting the light injection method could make it lasing a single wavelength of light, its side mode suppression ratio is insufficient in many applications [11]. We present an APC DFB laser to generate chirped microwave signals by a delayed self-heterodyne system. The generated signals provide a sweep range over 40 GHz, where the signal frequency maintains a strong correlation with the injection current (Ii). Provides an experimental basis for dynamic adjustment of the generated microwave signals
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