No abstract

No abstract

No abstract

A scheme for generating wideband optical frequency comb (OFC) is proposed and experimentally investigated based on a master-slave system. In such a system, a tunable optical resource and a distributed feedback semiconductor laser are utilized as master lasers (MLs), and their outputs provide dual optical injection (DOI) into a slave laser (SL) which is a 1550 nm multi-transverse mode vertical-cavity surface-emitting laser (1550 nm-VCSEL) operating at gain-switched state. For the 1550 nm-VCSEL biased at a relatively high current, two low-order transverse modes LP01 and LP11 can simultaneously lase and possess comparable powers. After loaded a large signal modulation, the 1550 nm-VCSEL can be driven into gain-switched state, and two separated sub-combs originating from two transverse modes can be generated. Through further introducing DOI to the gain-switched 1550 nm-VCSEL, the two sub-combs can link up to form an overall OFC under suitable operation parameters. The experimental results show that, through selecting optimized operating parameters, the bandwidth of the integral OFC within 10 dB amplitude variation can achieve 150.0 GHz. Additionally, the effects of the wavelengths of the two injection lights on the bandwidth of the overall OFC are also analyzed. INDEX TERMS Optical frequency comb, multi-transverse mode vertical-cavity surface-emitting laser, gain-switched, dual optical injection.

Passive Q-switched pulse lasers equipped with high quality gain media are expected to be the preferred UHF pulse sources containing THz pulse train. Based on a Yb: LuAG passively Q-switched laser pumped by a laser diode with a Yb ratio of 15at.% in Yb: LuAG, stable quasi-single longitudinal mode laser pulse trains and quasi-double longitudinal mode oscillation unstable pulse trains were observed experimentally, and the ultra-high-frequency (UHF) pulses excited by the high power unstable pulse trains were studied. The spectrum of the pulse train includes the low frequency spectrum with the base frequency below 500 KHz and the ultra-high frequency spectrum with the base frequency above 104 KHz. The base frequency change law of UHF spectrum with the increase of pump power conforms to the frequency doubling frequency principle of spectrum changing to higher frequency. With the increase of pump power, the fundamental frequency increases by 2n, reaching 0.32 THz in the experimental range of this paper. After the UHF pulse train is filtered at 1.25*105 KHz, a single UHF pulse train and its corresponding spectrum are obtained. The average peak power of UHF spectrum pulse increases with the increase of pump power.