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We demonstrate amplification of picosecond laser pulses to 40?mJ at a 2?kHz pulse repetition frequency (PRF) from a two-stage cryogenic chirped-pulse Yb:YAG amplifier, composed of a regenerative amplifier (RGA) and a two-pass booster amplifier. The RGA produces 8.2mJ of energy at 2kHz PRF and 13.2mJ at 1kHz PRF with excellent energy stability (approximately 0.3% rms) and beam quality (M(2)<1.1). Pulse stretching and compression are achieved by using a chirped fiber Bragg grating and a multilayer dielectric grating pair, respectively. Compressed 15?ps pulses from the RGA are obtained with a throughput efficiency of approximately 80% (approximately 6.5 mJ for 2kHz). The booster amplifier further amplifies the pulses to 40mJ at 2kHz PRF, and approximately 32 mJ, approximately 15 ps pulses are expected after compression. The amplifier chain seeded from a femtosecond Yb-fiber laser enables the optical self-synchronization between signal and pump in optical parametric chirped-pulse amplifier applications.

We show, numerically, that a single photon trapped by a soliton in a Kerr nonlinear medium can be transferred from one soliton to another when the captor soliton undergoes collision with a second soliton. Soliton collisions can also be used in this way to realize a beam splitter, as well as a mode-separating beam splitter, analogous to the usual polarizing beam splitter. We discuss briefly the feasibility of an optical fiber implementation and possible applications to quantum-information processing. DOI: 10.1103/PhysRevA.79.021802 PACS number͑s͒: 42.65.Tg, 42.50.Ex, 42.65.Jx, 42.79.Fm An optical soliton in a homogeneous medium such as a fiber is characterized, ideally, by undistorted propagation and elastic collisions. It arises because of an intensity-dependent change in the fiber's refractive index. For a temporal soliton, this refractive index change creates a traveling potential, which can serve as a waveguide for another optical pulse ͑the probe͒. Similarly, a spatial soliton imprints a waveguide in the medium, an effect that has been confirmed in both Kerr ͓1͔ and photorefractive media ͓2-5͔. In this Rapid Communication we show that when a soliton ͑the pump͒ collides with another soliton, the corresponding probe wave can be transferred almost perfectly from one soliton to another, or, depending on the conditions, split between two solitons, in perfect analogy to a beam splitter.In the quantum limit where the probe wave represents a single photon, these effects may find application to the storage, transport, and routing of qubits. Its delivery by a soliton means that a single photon will be subject to reduced dispersion compared with unguided transmission; its arrival time will be known more precisely and timing jitter reduced. This may be beneficial in quantum-communication applications as bit rates and propagation distances increase. Beyond this, the proposed implementation of a mode-splitting beam splitter suggests application to quantum computing using linear optics ͓6͔. Pittman et al. ͓7͔ show, in fact, that a polarizing beam splitter completely analogous to the mode-splitting beam splitter described here can be used to realize a controlled-NOT gate. Soliton-guided photons-in a fiber, for example-may thus provide a natural medium for optical quantum gate implementation.Following Manassah ͓8,9͔, de la Fuente and Barthelemy ͓1͔, and Ostrovskaya et al. ͓10͔ we model the system of interest with two coupled wave equations, the first being a standard cubic nonlinear Schrödinger equation for the pump, and the second a linear wave equation for the probe signal, which is assumed to be very much weaker than the pump. Thus, the propagation of the pump signal P͑z , t͒ is governed bywhere t is local time, z is propagation distance, ␤ 2p represents the group velocity dispersion of the pump, and ␥ p is a nonlinearity parameter. We neglect higher-order dispersion and assume a lossless medium with an instantaneous electronic response. We would like to use the exact two-soliton solution given in ͓11͔. To this end we...

We report the experimental observation of temporal vector soliton propagation and collision in a linearly birefringent optical fiber. To the best of the authors' knowledge, this is both the first demonstration of temporal vector solitons with two mutually incoherent component fields, and of vector soliton collisions in a Kerr nonlinear medium. Collisions are characterized by an intensity redistribution between the two components, and the experimental results agree with numerical predictions of the coupled nonlinear Schrödinger equation.

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A cryogenic Yb amplifier using two laser materials, Gd3Sc2Al3O12 and Y3Al5O12 (YAG), has been used to obtain 70 W average power at 5 kHz pulse repetition frequency; the output was compressed to 1.6 ps, compared with an input compressible to 1.4 ps. The gain broadening obtained by combining two media enables shorter pulses than using Yb:YAG alone but retains the power-scaling advantages of cryogenic Yb:YAG.

Beating noise in narrow-linewidth erbium-doped fiber ring lasers puts severe limitations on applications of the lasers. We demonstrate the suppression of beating noise in fiber ring lasers by using a semiconductor optical amplifier in the laser cavity, which acts as a high-pass filter. Two different ring structures are presented as examples to demonstrate this beating noise suppression.