We describe a fiber Raman amplifier for nanosecond and sub-nanosecond pulses centered around 1260 nm. The amplification takes place inside a 4.5-m-long polarization-maintaining phosphorus-doped fiber, pumped at 1080 nm by 3-ns-long pulses with a repetition rate of 200 kHz and up to 1.75 kW peak power. The input seed pulses are of sub-mW peak-power and minimal duration of 0.25 ns, carved off a continuous-wave laser with sub-MHz linewidth. We obtain linearly-polarized output pulses with peak-powers of up to 1.4 kW, corresponding to peak-power conversion efficiency of over 80%. An ultrahigh small-signal-gain of 90 dB is achieved, and the signal-to-noise ratio 3 dB below the saturation power is above 20 dB. No significant temporal and spectral broadening is observed for output pulses up to 400 W peak power, and broadening at higher powers can be reduced by phase modulation of the seed pulse. Thus nearly-transform-limited pulses with peak power up to 1 kW are obtained. Finally, we demonstrate the generation of pulses with controllable frequency chirp, pulses with variable width, and double pulses. This amplifier is thus suitable for coherent control of narrow atomic resonances and especially for the fast and coherent excitation of rubidium atoms to Rydberg states. These abilities open the way towards several important applications in quantum non-linear optics.
It attracts wide interest to seek universe saturable absorber covering wavelengths from near infrared to mid-infrared band. Multilayer black phosphorus, with variable direct bandgap (0.3-2 eV) depending on the layer number, becomes a good alternative as a universe saturable absorber for pulsed lasers. In this contribution, we first experimentally demonstrated broadband saturable absorption of multilayer black phosphorus from 1 μm to 2.7 μm wavelength. With the as-fabricated black phosphorus nanoflakes as saturable absorber, stable Q-switching operation of bulk lasers at 1.03 μm, 1.93 μm, 2.72 …
Using the Bogoliubov transformation in multi-frequency modes to describe the evolution of the non-degenerate signal and idler twin beams, we theoretically investigate the quantum noise properties of the pulse pumped high gain fiber optical parametric amplifiers (FOPA). The results show that the noise figure of the FOPA is generally greater than the 3 dB quantum limit unless the joint spectral function is factorable and the spectrum of the input signal well matches the gain spectrum in the signal band. However, the intensity difference noise of the twin beams, which weakly depends on the joint …
Black phosphorus, a newly emerged two-dimensional material, has attracted wide attention as novel photonic material. Here, multi-layer black phosphorus is successfully fabricated by liquid phase exfoliation method. By employing black phosphorus as saturable absorber, we demonstrate a passively Q-switched Er-doped ZBLAN fiber laser at the wavelength of 2.8 μm. The modulation depth and saturation fluence of the black phosphorus saturable absorber are measured to be 15% and 9 μJ/cm2, respectively. The Q-switched fiber laser delivers a maximum average power of 485 mW with corresponding pulse energ…
Motivated by the pursuit of a simple system to produce non-classical light sources for long- distance quantum communication, we generate for the first time an all-fiber source of pulsed twin beams in 1550 nm band by using a high gain fiber optical parametric amplifier. The noise of intensity difference of the twin beams is below the shot noise limit by 3.1 dB (10.4 dB after correction for losses). A detailed study reveals a number of limiting factors for higher noise reduction. Therefore, further noise reduction will be feasible once care is taken for these limiting factors.
Low-dimensional materials, due to their versatile properties are very interesting for numerous electronics and optoelectronics applications. Recently rediscovered black phosphorus, with a graphite-like structure can be exfoliated up to the single atomic layer. In contrary to graphene it possesses a direct band gap controllable by the number of stacked atomic layers. For those reasons, it is now intensively investigated. Here we demonstrate, that black phosphorus can serve as a broadband saturable absorber and can be used for ultrashort optical pulse generation. The mechanically exfoliated ~300…
We report high-energy mid-infrared pulse generation by Q-switching of dysprosium-doped fiber lasers for the first time. Two different modulation techniques are demonstrated. Firstly, using active acousto-optic modulation, pulses are produced with up to 12 μJ energy and durations as short as 270 ns, with variable repetition rates from 100 Hz to 20 kHz and central wavelengths tunable from 2.97 to 3.23 μm. Experiments are supported by numerical modeling, identifying routes for improved pulse energies and to avoid multi-pulsing by careful choice of modulator parameters. Secondly, we demonstrate pa…
With the proposal of dual-wavelength pumping (DWP) scheme, DWP Er:ZBLAN fiber lasers at 3.5 um have become a fascinating area of research. However, limited by the absence of suitable saturable absorber, passively Q-switched and mode-locked fiber lasers have not been realized in this spectral region. Based on the layer-dependent bandgap and excellent photoelectric characteristics of black phosphorus (BP), BP is a promising candidate for saturable absorber near 3.5 um. Here, we fabricated a 3.5-um saturable absorber mirror (SAM) by transferring liquid-phase exfoliated BP flakes onto a gold-coate…
We report on new simple and efficient multipass amplifiers using prisms or corner cubes to perform several passes in different planes of incidence. This scheme provides an optimized overlap between the signal passes and the pumped volume. We investigated our amplification geometry with Nd:YAG and Nd: YVO4 crystals : the use of a low doped (0.3%) Nd:YVO4 crystal allowed better thermal behaviour and higher performances. We amplified a pulsed microlaser (110 mW of average power at 1064 nm) and obtained a diffraction-limited output beam with an average power of 5.7 W for 15 W of pump power and a s…
A power enhancement optical cavity is a compelling means of realizing a pulsed laser with a high peak power and high repetition frequency, which is not feasible using a simple amplifier scheme. However, a precise feedback system is necessary for maintaining the narrow resonance condition of the optical cavity; this has become a major technical issue in developing such cavities. We have developed a new approach that does not require any active feedback system, by placing the cavity in the outer loop of a laser amplifier. We report on the first demonstration of a mode-locked pulse oscillation us…
The regular spatial filters comprised of lens and pinhole are essential component in high power laser systems, such as lasers for inertial confinement fusion, nonlinear optical technology and directed-energy weapon. On the other hand the pinhole is treated as a bottleneck of high power laser due to harmful plasma created by the focusing beam. In this paper we present a spatial filter based on angular selectivity of Bragg diffraction grating to avoid the harmful focusing effect in the traditional pinhole filter. A spatial filter consisted of volume phase gratings in two-pass amplifier cavity we…
Phase sensitive amplifiers (PSAs) have the potential to empower substantial advances in emerging generations of optical communication systems as well as classical and quantum on-chip signal processing. The core building block of a PSA is a nonlinear medium. While the second-order nonlinearity ($χ^{(2)}$) is stronger than the third-order nonlinearity ($χ^{(3)}$), it is used less often in semiconductors for parametric amplification owing to the challenges of effectively phase matching the interacting waves as well as two-photon absorption of the pump. In this work, we demonstrate the successful …
A scalable on-chip single-photon source at telecommunications wavelengths is an essential component of quantum communication networks. In this work, we numerically construct a pulse-regulated single-photon source based on an optical parametric amplifier in a nanocavity. Under the condition of pulsed excitation, we study the photon statistics of the source using the Monte Carlo wave-function method. The results show that there exits an optimum excitation pulse width for generating high-purity single photons, while the source brightness increases monotonically with increasing excitation pulse wi…
We demonstrate a monolayer graphene based passively Q-switched fiber laser with three-stage amplifiers that can deliver over 80 W average power at 1064 nm. The highest average power achieved is 84.1 W, with pulse energy of 1.67 mJ. To the best of our knowledge, this is the first time for a high power passively Q-switched fiber laser in the 1 um range reported so far. More importantly, the Q-switched fiber laser operates stably during a week few-hours-per-a-day tests, which proves the stability and practical application value of graphene in high power pulsed fiber lasers.
We demonstrate a simple method to obtain accurate optical waveforms with a GHz-level programmable modulation bandwidth and Watt-level output power for wideband optical control of free atoms and molecules. Arbitrary amplitude and phase modulations are transferred from microwave to light with a low-power fiber electro-optical modulator. The sub-milliWatt optical sideband is co-amplified with the optical carrier in a power-balanced fashion through a tapered semiconductor amplifier (TSA). By automatically keeping TSA near saturation in a quasi-continuous manner, typical noise channels associated w…
The performance of fiber laser systems has drastically increased over recent decades, which has opened up new industrial and scientific applications for this technology. However, currently a number of physical effects prevents further power scaling. Coherent combination of beams from multiple emitters has been established as a power scaling technique beyond these limitations. It is possible to increase the average power and, for pulsed laser systems, also parameters such as the pulse energy and the peak power. To realize such laser systems, various aspects have to be taken into account which i…
We present an entirely fiber based laser source for non-linear imaging with a novel approach for multi-color excitation. The high power output of an actively modulated and amplified picosecond fiber laser at 1064 nm is shifted to longer wavelengths by a combination of four-wave mixing and stimulated Raman scattering. By combining different fiber types and lengths, we control the non-linear wavelength conversion in the delivery fiber itself and can switch between 1064 nm, 1122 nm, and 1186 nm on-the-fly by tuning the pump power of the fiber amplifier and modulate the seed diodes. This is a prom…
Integrated femtosecond pulse and frequency comb sources are critical components for a wide range of applications. The leading approaches for on-chip pulse generation rely on mode locking inside microresonator with either third-order nonlinearity or with semiconductor gain. These approaches, however, are limited in noise performance, wavelength tunability and repetition rates. Alternatively, sub-picosecond pulses can be synthesized without mode-locking, by modulating a continuous-wave (CW) single-frequency laser using a cascade of electro-optic (EO) modulators. This method is particularly attra…
