In this paper, we report for the first time, control of the output-pulse-energy characteristics of a CW pumped, high repetition rate, passively Q-switched Nd:YVO4/Cr:YAG microchip laser by using the large reduction of the stimulated emission cross-section of the Nd:YVO4 crystal on increasing its temperature.
We demonstrate our results by showing the very significant improvement in the supercontinuum generated in a photonic crystal fiber by the microchip laser output, when the Nd:YVO4 crystal temperature is increased from 25℃ to 55℃.
The results will be very useful for achieving very compact, high repetition rate and high pulse energy lasers for various applications.
Pulse-by-pulse single-shot spectrum measurement can be realized using the time stretch dispersive Fourier Transform technique. In this paper, we report a fully integrated and modular pulse-by-pulse single-shot optical spectrum analyzer (PS-OSA) system. Many modules including a picosecond gain-switched laser, multiple fibers with different chromatic dispersions, high-power optical amplifiers, a clock-generator, a photodetector and a digitizer are integrated into a main-frame. These modules are standard in size and can be replaced to improve the performance or changed to adapt the system to different applications. Here, we present the specification of this single-platform PS-OSA and successfully demonstrate high throughput measurement of the transmission spectrum of electroabsorption optical modulators with 11.7 ns refresh time.
The time stretch dispersive Fourier Transform (TS-DFT) technique based on a fiber chromatic dispersion is a powerful tool for pulse-by-pulse single-shot spectrum measurement for highrepetition rate optical pulses. The distributed feedback laser diode (DFB-LD) with the gain switch operation can flexibly change the pulse repetition frequency (PRF). In this paper, we newly introduce a semiconductor gain-switched DFB-LD operating from 1 MHz up to 1 GHz PRF into the TS-DFT based spectrum measurement system to improve the flexibility and the operability. The pulse width can be below 2 ps with a pulse compression technique. We successfully measure the spectrum of each optical pulse at 1 GHz, 100 MHz, and 10 MHz PRF, and demonstrate the flexibility of the measurement system.
Single-shot and long record length spectrum measurements of high-repetition-rate optical pulses are essential for research on nonlinear dynamics as well as for applications in sensing and communication. To achieve a continuous measurements we employ the Time Stretch Dispersive Fourier Transform. We show single-shot measurements of millions of sequential pulses at high repetition rate of 1 Giga spectra per second. Results were obtained using -100 ps/nm dispersive Fourier transform module and a 50 Gsample/s real-time digitizer of 16 GHz bandwidth. Single-shot spectroscopy of 1 GHz optical pulse train was achieved with the wavelength resolution of approximately 150 pm. This instrument is ideal for observation of complex nonlinear dynamics such as switching, mode locking and soliton dynamics in high repetition rate lasers.
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