High-Speed Single-Photon Detection with Avalanche Photodiodes in the Near Infrared

As the requisite optical components in quantum information processing, single-photon detectors of high performance at the near-infrared wavelengths are in urgent need. In this paper, we review our recent development in high-speed single-photon detection with avalanche photodiodes, increasing the working repetition frequency up to GHz. Ingenious techniques, such as capacitance-balancing, self-differencing, low-pass filtering, and frequency up-conversion, were employed to achieve high-speed single-photon detection with high detection efficiency and low error counts, offering facility for many important applications, such as laser ranging and imaging, quantum key distribution at GHz clock rate

Fiber-Based High-Power Supercontinuum and Frequency Comb Generation

Ultrafast optics has been a rich research field, and picosecond/femtosecond pulsed laser sources seek many applications in both the areas of fundamental research and industrial life. Much attention has been attached to fiber lasers in recent decades as they offering various superiorities over their solid-state counterparts with compact size, low cost, and great stability due to the inherent stability and safety of the waveguide structures as well as high photoelectric conversion efficiency. Fiber-based sources of ultrashort and high-peak/high-average optical pulses have become extremely important for high-precision laser processing while sources whose carrier-envelop offset and repetition rate are stabilized can serve as laser combs with applications covering many research areas, such as precision spectroscopy, optical clock, and optical frequency metrology. For the application as laser combs, four parts as fiber laser, broadband supercontinuum, nonlinear power amplification, and repetition rate stabilization must be concerned. This chapter is intended to give a brief introduction about the achievement of the four technologies mentioned above with different experimental setups, recently developed such as divided-pulse amplification (DPA) in emphasize. Moreover, detailed descriptions of the experimental constructions as well as theoretical analyses about the phenomena they produced are also involved

Polymer Micro/Nanofibre Waveguides for Optical Sensing Applications

This chapter focuses on polymer micro/nanofibre (PMNFs) waveguides and their applications in sensing applications. The PMNFs are functionalized by doping with dyes or blending with solvated polymers before the drawing process. Based on the evanescent wave-coupling technique, the excitation light is efficiently coupled into the PMNFs using silica-fibre tapers and guided along the long-length PMNF waveguides. Due to the tight confinement, the interaction of light with PMNFs is significantly enhanced. Intriguing advantages such as enhanced excitation efficiency, low excitation power operation and high photostability are obtained. On the basis of the optical response when exposed to specimens, functionalized PMNFs are used for humidity, NO2, and NH3 detection with high sensitivity and fast response. By using a simple and low-cost nanoimprinting technique, PMNF Bragg gratings are also demonstrated for strain sensing with a high sensitivity of −2.5 pm/με

Narrow-band single-photon emission in the near infrared for quantum key distribution

We report on the observation of single colour centers in natural diamond samples emitting in the near infrared region when optically excited. Photoluminescence of these single emitters have several striking features, such as a narrow-band fully polarized emission (FWHM 2 nm) around 780 nm, a short excited-state lifetime of about 2 ns, and perfect photostability at room temperature under our excitation conditions. We present a detailed study of their photophysical properties. Development of a triggered single-photon source relying on this single colour centre is discussed in the prospect of its application to quantum key distribution.Comment: 9 page

Breathing dissipative solitons in mode-locked fiber lasers

Dissipative solitons are self-localized coherent structures arising from the balance between energy supply and dissipation. Besides stationary dissipative solitons, there are dynamical ones exhibiting oscillatory behavior, known as breathing dissipative solitons. Substantial interest in breathing dissipative solitons is driven by both their fundamental importance in nonlinear science and their practical applications, such as in spectroscopy. Yet, the observation of breathers has been mainly restricted to microresonator platforms. Here, we generate breathers in a mode-locked fiber laser. They exist in the laser cavity under the pump threshold of stationary mode locking. Using fast detection, we are able to observe the temporal and spectral evolutions of the breathers in real time. Breathing soliton molecules are also observed. Breathers introduce a new regime of mode locking into ultrafast lasers. Our findings may contribute to the design of advanced laser sources and open up new possibilities of generating breathers in various dissipative systems

Striking nonlinear dynamics of mode-locked fibre lasers

We report on the real-time observation of various remarkable nonlinear phenomena in mode-locked fibre lasers. These include the build-up of dissipative solitons and soliton molecules, collision-induced soliton explosions, and the excitation and dynamics of breathing dissipative solitons and breather molecular complexes. Numerical simulations of the laser model support our experimental findings