Abstract:
The possibility of microwave pulses generation in the photovoltaic mode by monolithic triple-junction AlGaAs/GaAs photoconverters of laser radiation grown by molecular beam epitaxy has been demonstrated. In monolithic triple-junction $p$–$i$–$n$ AlGaAs/GaAs photoconverters, a significant increase in output peak pulse power and fast performance in the subnanosecond range has been achieved compared to
single-junction $p$–$i$–$n$ photoconverters. When pulsed laser radiation at a wavelength of 850 nm with a peak power of $<$ 5 W and full width at half maximum (FWHM) of 140 ps was injected from the optical fiber, photoresponse pulses with amplitude $U_{\mathrm{max}}$ = 2.7 V, peak power $P_{peak}$ = 21.6 dBm, and FWHM $\le$ 750 ps were obtained. A module of two series-connected photoconverters provided output pulses with an amplitude of $U_{\mathrm{max}}$ = 3.4 V, power $P_{peak}$ = 23.7 dBm and FWHM $\le$ 420 ps. It is shown that the module of four monolithic triple-junction photoconverters is capable of forming a bipolar microwave pulse with parameters $U_{\mathrm{max}}$ = 6.4 V, $P_{peak}$ = 29.1 dBm, FWHM $\le$ 1 ns, bandwidth up to 1.4 GHz and the main carrier frequency of 0.8 GHz. The numerical modeling showed a fairly good agreement between the measured and calculated photoresponse pulses shapes of photoconverters.
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