Pulsed Raman Laser Research Articles

Raman fingerprints on a spinor BEC

We present examples of ring structures that arise in a 87Rb spinor condensate through the application of Raman laser pulses that couple the internal spin states of the F = 2 ground state manifold. The appearance of fringes within the context of the population transfer dynamics is discussed, and several pulse protocol options are compared.

Dependence of sensitivity of atom interferometer gravimeters on the Raman laser pulse sequences

We investigate the dependence of the sensitivity of atom interferometer gravimeter on the Raman laser pulse sequence. The sensitivity of atom gravimeter can be adjusted by changing the pulse duration. Under the standard pulse configuration condition, the atom interferometer with four pulses is insensitive to the gravity if only gravity and its first order gradient are taken into account. The three-pulse Raman atom interferometer gravimeter displays best sensitivity. Atom interferometers with more than four Raman pulses show poorer sensitivity.

Optical field dynamics in a wavelength-versatile, all-solid-state intracavity cascaded pulsed Raman laser

Monitoring the optical field energies in an intracavity cascaded crystalline pulsed Raman laser enables us to probe the dynamics and optimise the performance of the laser, which produces up to 2.1 W average output power at 4 wavelengths between 532 and 636 nm selectable by simple angle tuning.

Modelling of passively Q-switched lasers with intracavity Raman conversion

We present a model of passively Q-switched Raman lasers by utilizing the rate equations. The intracavity fundamental photon density, Raman photon density and the initial population-inversion density of the gain medium are assumed to be of Gaussian spatial distributions. These rate equations are normalized by introducing some synthetic parameters and solved numerically, and a group of general curves are generated. From these curves we can understand the dependence of the Raman laser pulse characteristics on the parameters about the pumping, the gain medium, the Raman medium and the resonator. An illustrative calculation for a passively Q-switched Nd3+:GdVO4 self-Raman laser is presented to demonstrate the usage of the curves and related formulas.

Criteria for exact qudit universality

We describe criteria for implementation of quantum computation in qudits. A qudit is a d-dimensional system whose Hilbert space is spanned by states |0>, |1>,... |d-1>. An important earlier work of Mathukrishnan and Stroud [1] describes how to exactly simulate an arbitrary unitary on multiple qudits using a 2d-1 parameter family of single qudit and two qudit gates. Their technique is based on the spectral decomposition of unitaries. Here we generalize this argument to show that exact universality follows given a discrete set of single qudit Hamiltonians and one two-qudit Hamiltonian. The technique is related to the QR-matrix decomposition of numerical linear algebra. We consider a generic physical system in which the single qudit Hamiltonians are a small collection of H_{jk}^x=\hbar\Omega (|k><j|+|j><k|) and H_{jk}^y =\hbar\Omega (i|k><j|-i|j><k|). A coupling graph results taking nodes 0,... d-1 and edges j<->k iff H_{jk}^{x,y} are allowed Hamiltonians. One qudit exact universality follows iff this graph is connected, and complete universality results if the two-qudit Hamiltonian H=-\hbar\Omega |d-1,d-1><d-1,d-1| is also allowed. We discuss implementation in the eight dimensional ground electronic states of ^{87}Rb and construct an optimal gate sequence using Raman laser pulses.

Demonstration of a silicon Raman laser

We report the demonstration of the first silicon Raman laser. Experimentally, pulsed Raman laser emission at 1675 nm with 25 MHz repetition rate is demonstrated using a silicon waveguide as the gain medium. The laser has a clear threshold at 9 W peak pump pulse power and a slope efficiency of 8.5%.

Complete population transfer between two Bose-Einstein condensates induced by nonlinear laser coupling

We investigate atomic population dynamics of two Bose-Einstein condensate (BEC) states that are in different traps or in the same trap and are optically coupled through a common excited state by Raman laser pulses. For large interatomic interactions, almost all of the atoms that are initially in one of the traps (or one of the internal states) are either completely transferred into the other state or stay in the initially occupied state after the laser pulses, and the atoms (populations) are never distributed to both condensate states at the same time. Applications to the atomic logic gate and to output couplers of the atom laser are pointed out.

Efficient Raman shifting of picosecond pulses using BaWO 4 crystal

Stimulated Raman scattering of picosecond pulses was investigated in a new BaWO 4 Raman crystal and was compared with SRS in well known KGd(WO 4) 2 and KY(WO 4) 2 crystals. The first and second harmonic output of a mode-locked Nd:YAG laser system was used as a pump source. Due to transient behaviour, high value of BaWO 4 steady state Raman gain is reduced by a factor of 2.5 for picosecond pump pulses (28 and 40 ps) but remains still higher than that in KGd(WO 4) 2 crystal. Maximum first and second Stokes conversion efficiencies for BaWO 4 in a single-pass arrangement were measured to be 30% and 15%, respectively. Measurements of a temporal pulse length showed that the first Stokes pulse was twice as short as the pump pulse. Barium tungstate can thus be considered as a unique Raman crystal for wide variety of pump pulse duration from nanoseconds to picoseconds for the generation of the frequency shifted Raman laser pulses.

All solid-state diode-pumped Raman laser with self-frequency conversion

Operation of an all solid-state compact pulsed Raman laser pumped by a continuous-wave laser diode is demonstrated. The Stokes and anti-Stokes radiations of stimulated Raman scattering at the 1.181 and 0.973 μm wavelengths, respectively, are generated as a result of self-frequency conversion of the 1.067 μm laser radiation in a Nd3+:KGd(WO4)2 crystal. With Q-switched operation, the Raman laser threshold corresponds to 230 mW of a laser diode light power. The output power of 4.8 mW is achieved at the Stokes wavelength with a kilohertz repetition rate.

Q-switch pumped InSb spin-flip raman laser action under pulsed electric field conditions

Temporal synchronization of a Q-switch spin-flip Raman laser pulse (SFR) with a voltage pulse across an InSb sample leads to an enhancement of the Stokes output and to a shortening of the spin-flip pulse duration. During the end of the voltage pulse with a fall time ⩽ 30 ns, the Stokes output power increased by a factor 2–3 while the SFR pulse duration decreased to 50 ns.

Time-resolved pump depletion in n-InSb Raman spin-flip laser

We have observed a strong transient optical absorption in n-InSb (n=1016 cm−3) induced by an intense (2 MW cm−2) 10.6-μm laser beam at 2 K. Detailed studies of the time history of the transmitted 10.6-μm beam and the spin-flip Raman laser pulse produced in the InSb show that the 10.6-μm absorption lasts for ≳100 ns, and that spin-flip lasing occurs only at the beginning of the intense portion of the 10.6-μm pump pulse and after the absorption has disappeared.

Power output of a pulsed Raman laser with saturable excitation

A theoretical expression is obtained for the time dependence of the Stokes power output of a pulsed Raman laser, the pump pulse duration being comparable to the relaxation time of the Raman excitation and the output saturation limited. A rate-equation approach is employed, and the pump beam is assumed to have a Gaussian intensity distribution. The theory is developed in terms of the practical example, stimulated spin-flip Raman scattering in InSb.

Electric-field-induced transient spin-flip Raman laser pulses in InSb

An InSb spin-flip Raman laser pumped continously by a carbon monoxide laser near 5.2 μm has produced Stokes pulses of ≲ 10−9-sec duration when an electric field of a few V/cm was applied or removed from the sample. This effect is interpreted in terms of a transient Raman gain, which occurs when electrons are heated or allowed to cool in the conduction band.