We report a passively Er3+-doped mode-locked fiber laser based on repetition rate multiplication, in which a three-stage Mach Zehnder interference structure is employed as a repetition rate multiplier. The initial soliton pulses are generated from a ring cavity with a fundamental repetition rate of 102.70 MHz, which is a seed laser. When the intrinsic frequency of repetition rate multiplier is almost aligned with a variable optical delay line, the initial repetition rate output from a seed laser, is lifted from 100.20 MHz to 801.03 MHz. This result demonstrates a method to achieve high repetition rate (> 500 MHz) pulse lasers, which avoids the limitation of cavity length on the repetition rate.
Low-time jitter optical pulses are widely used in precision ranging, photonic microwave generation, optical frequency comb generation, and photonic sampling. In order to obtain highly stable optical pulses at 1560 nm with an ultra-high pulse frequency of approximately 10GHz, a self-regeneratively ultrafast mode-locked laser with a polarization-maintaining fiber cavity is demonstrated in this paper. The laser adopts a section of polarization-maintaining erbium-doped fiber as the gain medium, a lithium niobate phase modulator as the active modulation device, and the rest of the resonant cavity are composed of passive polarization-maintaining fibers. This results in a total ring cavity length of about 10.7 m. The ring cavity can stimulate multiple longitudinal modes under free running conditions. One of these longitudinal mode frequencies is selected through using a self-built clock extraction and recovery module to generate RF signal with a frequency of 10 GHz. The amplified RF signal at 10 GHz drives the phase modulator and modulates the optical field in the cavity, which results in a stable self-regeneratively mode-locked pulse in the entire laser loop. It quickly achieves a stable ultrafast mode-locked state with a low timing jitter without any external RF reference. A pulse frequency of 10.0076 GHz and a pulse width of 3.14 ps were obtained, together with a side-mode suppression ratio of more than 80 dB and a phase noise of about -110 dBc/Hz@10 kHz. The characteristics of this laser, such as long-time stability, repetition rate, and spectral stability, are investigated in detail. Besides, some typical lasing states in experiments are compared and analyzed.
Since the growing needs of broadband optical frequency combs (OFCs) in many applications, in this paper, a carrier suppressed dual-sideband modulation recirculating frequency shift loop (RFSL) with an additional piece of highly nonlinear fiber (HNLF) is numerically investigated. The numerical results indicate that, thanking to the RFSL scheme, the frequency spacing of OFC can be both widely and precisely tuned over the range of 0.5 - 40 GHz. Moreover, the comb lines generated from RFSL can be then efficiently increased, using four wave mixing effect of HNLF in the simulation, thus the spectrum is further broadened. This work contributes to an effective and compact RFSL scheme for a frequency tunable OFC generation with broadband spectrum.
In this paper, a broadband microwave photonic channelized receiver based on optical frequency comb (OFC) injection locking technology is illustrated. The simulation results show that, with more than 80 comb lines generated from OFC, this receiver enables channelized scanning and reception of broadband signal up to 40 GHz with instantaneous bandwidth of 1 GHz. Meanwhile, the channels selected using optical injection locking (OIL) technology, perform high gain and low phase noise with suppression ratio between the selected comb line and other comb lines is 28.7 dB. Due to OIL technology, the wideband tunability of this receiver would not depend on the optical filter or demultiplexer, and the band limitation and operation resolution introduced by optical components are broken through. The OIL technology also lead to the architecture of receiver more compact and feasible in practical.
Many important molecules show strong characteristic vibrational transitions in the mid-infrared (MIR) part of the electromagnetic spectrum. This leads to applications in spectroscopy, chemical and bio-molecular sensing, security and industry, especially over the mid- and long- wave infrared atmospheric transmission windows of 3-5 μm and 8-13 μm. In this paper, we review some of our more recent experimental and simulation work aimed at developing new light sources based on chalcogenide glass optical fibres that can help us utilize this spectral region for biomedical applications. This includes the development of supercontinuum and bright luminescent sources and our progress towards fibre-based lasers. We place these developments in the context of MIR imaging and spectroscopy in order to show how they bring the promise a new era in healthcare and clinical diagnostics.
Recently, the concept of random fiber lasers has attracted a great deal of attention for its feature to generate incoherent light without a traditional laser resonator, which is free of mode competition and insure the stationary narrow-band continuous modeless spectrum. In this Letter, we reported the first, to the best of our knowledge, optical parametric oscillator (OPO) pumped by an amplified 1070 nm random fiber laser (RFL), in order to generate stationary mid-infrared (mid-IR) laser. The experiment realized a watt-level laser output in the mid-IR range and operated relatively stable. The use of the RFL seed source allowed us to take advantage of its respective stable time-domain characteristics. The beam profile, spectrum and time-domain properties of the signal light were measured to analyze the process of frequency down-conversion process under this new pumping condition. The results suggested that the near-infrared (near-IR) signal light ‘inherited’ good beam performances from the pump light. Those would be benefit for further develop about optical parametric process based on different pumping circumstances.
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