Cavity Arrangement Research Articles

Generation of atomic-squeezed states in an optical cavity with an injected squeezed vacuum.

We study the generation of atomic-squeezed states in an optical cavity. The cavity encloses a pair of two-level atoms and is coupled to a broadband squeezed vacuum. Using the bad-cavity limit, cavity field is adiabatically eliminated to obtain the equations of motion for collective atomic operators. These equations are then employed to obtain the atomic density-matrix elements and to study the generation of atomic-squeezed states in the steady state. To characterize atomic-squeezed states we use the squeezing parameter defined recently by Wineland et al. [Phys. Rev. A 46, 6797 (1992)] for spectroscopic purposes. The aforementioned parameter is also compared with the squeezing parameter obtained from the uncertainty principle satisfied by the collective atomic operators. We show that in a cavity arrangement, unlike free space, atomic-squeezed states can be generated only for a restricted range of values of the parameters \ensuremath{\lambda} and N which characterize the cavity and the squeezed field driving the cavity, respectively. \textcopyright{} 1996 The American Physical Society.

Recent Performance Results of the National Ignition Facility Beamlet Demonstration Project

The laser driver for the National Ignition Facility will be a departure from previous inertial confinement fusion laser architecture of a master oscillator single pass power amplifier (MOPA) design. The laser will use multi-segment Nd:Glass amplifiers in a multipass cavity arrangement, which can be assembled into compact and cost effective arrays to deliver the required multi- megajoule energy to target. A single beam physics prototype, the Beamlet, has been in operation for over two years and has demonstrated the feasibility of this architecture. We present a short review of Beamlet`s performance and limitations based on beam quality both at its fundamental and frequency converted wavelengths of 1.053 and 0.351 {mu}m.

An Experimental Study Evaluating Macroscopic Cavity Interactions as a Model of Microvoid Ductility

An experimental study of the interactions between macroscopic cavities was conducted. The goal was to determine simple cavity arrangements producing deformations similar to commonly observed features of ductile fracture. The production of cavity-centered fracture surface features and ligament thinning, representative of the type observed around and between microvoids on ductile fracture surfaces, were the specific objectives of this macroscopic study. The specimens employed were cylindrical tension specimens containing from one to six coplanar radial holes, with spherical end profiles, located at the center of the specimen and either zero or one cylindrical holelocated on the longitudinal axis of the specimen. The results of this parametric study identified the two specimens that best produced the desired features. The load-displacement results of these experiments also illustrate the effect of cavity geometry on the net strength and ductility of the array system. Specimens of these designs provide a future basis for simple and economical model studies of void interactions.

Influence of process parameters on diamond film CVD in a surface-wave driven microwave plasma reactor

The influence upon diamond film chemical vapour deposition of operator-set process parameters in a novel microwave plasma reactor is examined. The new reactor operates with a discharge sustained by an electromagnetic surface wave in a non-conventional configuration that yields a plasma hemisphere in the vicinity of the substrate. The basic advantages of this reactor compared with “plasma-ball” systems in resonant cavity and bell-jar arrangements have been reported in a previous paper. The present paper provides the results of a parametric study of the quality of diamond films as well as of the gas temperature and hydrogen atom concentration in the discharge as functions of methane and oxygen concentrations, substrate position and temperature, gas pressure, and microwave power density absorbed in the plasma. The conditions optimizing both maximum growth rate and film quality correspond to a total gas pressure of 15 Torr (2 kPa), with a 0.75% CH 4 content and a substrate temperature of 930 °C, although good quality films can be achieved over a broader range, at gas pressures between 10 and 60 Torr (1.33–8 kPa), with a 0.25–0.75% CH 4 content, and with substrate temperatures in the range 870–980 °C.

Widely tunable, single-longitudinal-mode, diodepumped CW Cr:LiSAF laser

Wide range tunability of 148 nm, with a maximum output power of 25 mW has been obtained from a diode pumped CW Cr:LiSAF laser operated in single-longitudinal mode, using a coupled cavity arrangement with a diffraction grating. Wavelength tuning with an expanded beam on the grating by an anamorphic prism pair is effective for linewidth narrowing.

Ti: Sapphire Pumped Femtosecond Optical Parametric Oscillator Exhibiting Soliton Formation

Abstract The configuration and operation of a singly resonant Ti: sapphire pumped optical parametric oscillator (OPO) based on KTP is discussed. Cavity arrangements with and without dispersion compensation are described and the generation of sub-40 fs transform-limited pulses is highlighted. Evidence for soliton pulse formation in the OPO is presented and good quantitative agreement with existing theory is implied. Results of amplitude and phase noise measurements of the OPO are given and compared with those of the pump laser. Generation of pulses at several visible wavelengths by non-phase-matched processes is also briefly discussed.

Design and performance of a simple 2 joule KrF laser

We describe the design and performance details of a high-energy KrF excimer laser, operating at 248 nm, suitable for generating laser-produced plasma X-ray sources for applications such as soft X-ray contact microscopy. The UV pre-ionized, discharge excited laser is relatively simple and inexpensive to construct. Using a plane-plane (i.e. Fabry-Perot) cavity arrangement, an output energy of 2.24 J per pulse has been achieved.

A novel microwave plasma cavity assembly for atomic emission spectrometry

The design approach that leads to a simple new cavity structure for a microwave discharge used for analytical chemistry is outlined. The design and construction of a totally new and efficient microwave cavity assembly, namely an integrated microwave generator/cavity combination, operated at 2.45 GHz, and preliminary operating conditions that exceed certain operational capabilities of the existing Beenakker and surfatron arrangements are described. The feasibility of operating such a microwave plasma cavity arrangement to form plasma discharges in argon, helium, nitrogen, air and oxygen at atmospheric pressure for atomic emission spectrometry has been demonstrated. The generation of an oxygen microwave induced plasma (MIP) discharge with conventional tubes used routinely in the argon or helium MIP suggests its application in spectrochemical analysis. The introduction of wet aerosols, because of the excellent resistance to detuning caused by changes in plasma density, can be accomplished by using direct solution nebulization with no desolvation system and with a typical inductively coupled plasma nebulizer-spray chamber.

Continuously self-mode-locked Ti:sapphire laser that produces sub-50-fs pulses

An external cavity coupled to a dispersion-compensated, self-mode-locked Ti:sapphire laser is shown to maintain cw mode locking to produce pulses as short as 47 fs. The same cavity arrangement is also shown to generate transform-limited pulses of 2-ps duration in the regime of linear external cavity mode locking.

Coupled-cavity passive mode-locked injection laser

Experimental results on the observation of the self-initiating passive mode-locking operation of an injection laser with a nonlinear external-coupled-cavity configuration are presented. Michelson and Fabry-Perot cavity arrangements with similar laser diodes as both the gain medium and nonlinear element have been investigated. This technique can be used for generating short pulses with ultrahigh repetition rates without utilizing both high-modulation bandwidth laser diodes and ultrafast electronics, which do not require special saturable absorbers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Measurement of microwave surface resistance of patterned superconducting thin films

A simple and versatile measurement technique has been demonstrated for characterization of thin film superconductors and the substrates on which they are deposited. Unlike other state of the art measurements that characterize only the top layer of unpatterned thin films in end-plate replacement or perturbation-type cavity arrangements, we test the sample under conditions very close to those of actual microwave circuit applications. Measurements on a laser deposited, thin-film YBCO superconductor, patterned in the form of a meander line on a LaAlO3 substrate, show a microwave surface resistance one order of magnitude lower than that of copper at 79 K and 11 GHz. At 1.4 GHz and 79 K, an improvement by over two orders of magnitude is observed. This is the first demonstration of superior microwave performance of a comb filter structure using a HTS thin film.

A study of the collapse of arrays of cavities

This paper describes a method for examining the collapse of arrays of cavities using high-speed photography and the results show a variety of different collapse mechanisms. A two-dimensional impact geometry is used to enable processes occurring inside the cavities such as jet motion, as well as the movement of the liquid around the cavities, to be observed. The cavity arrangements are produced by first casting water/gelatine sheets and then forming circular holes, or other desired shapes, in the gelatine layer. The gelatine layer is placed between two thick glass blocks and the array of cavities is then collapsed by a shock wave, visualized using schlieren photography and produced from an impacting projectile. A major advantage of the technique is that cavity size, shape, spacing and number can be accurately controlled. Furthermore, the shape of the shock wave and also its orientation relative to the cavities can be varied. The results are compared with proposed interaction mechanisms for the collapse of pairs of cavities, rows of cavities and clusters of cavities. Shocks of kbar (0.1 GPa) strength produced jets ofc.400 m s−1velocity in millimetre-sized cavities. In closely-spaced cavities multiple jets were observed. With cavity clusters, the collapse proceeded step by step with pressure waves from one collapsed row then collapsing the next row of cavities. With some geometries this leads to pressure amplification. Jet production by the shock collapse of cavities is suggested as a major mechanism for cavitation damage.

A Comment on Nonlinear Optics Using Surface Plasmon-polaritons

Abstract Theories of nonlinear effects associated with the surface plasmonpolariton (SPP) mode have centred on the enhanced electric field localized at the metal/dielectric interface. Although SPPs do indeed present potentially large field enhancements without the need for a Fabry-Perot resonator, the primary nonlinear effect will almost invariably be thermally induced. Unlike a resonant cavity arrangement, the SPP resonance is a resonant absorption of the incident power into Joule heating of the metal.

Inclusion of water by a crown amide. First crystal structure of a respective host-guest combination

Crown amide (1) forms a stoicheiometric 1:1 inclusion complex with water, the X-ray crystal structure of which is reported. Crystals of1 · H2O are triclinic, space groupP1, witha=7.503(1),b=11.394(3),c=13.443(2) A, α=107.066(18), β=96.627(10), γ=106.377(14)°, andZ=2.R F =0.039 for 1697 MoKα reflections [I>3σ(I)] measured at 24°C. The structure features a hydrogen bonded hostguest relationship with concrete1 · H2O units. Hydrogen bonds are between the water oxygen and O(4), N(4), respectively. The crystal packing shows a cavity arrangement of four ligands around each water molecule.

Single lobe operation of a 40-element laser array in an external ring laser cavity

Single lobe operation of a 40-element GaAlAs gain guided coupled stripe array emitting 500 mW cw is obtained in an external ring laser cavity. The cavity arrangement is equivalent to self-injection locking of the array by its own output, which is first spatially filtered by a single mode fiber. Diffraction-limited lobe width of 0.13° and single mode operation are demonstrated with a 90 mW single mode fiber output.

Femtosecond pulse generation in the red/deep red spectral region

Optical pulses as short as 55 fs in duration have been generated near 675 nm in a synchronously pumped, hybridly mode-locked, sulforhodamine 101 dye laser. Hybrid mode locking of rhodamine <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</tex> in the same cavity arrangement yielded 187 fs pulses at 650 nm.

Small line width nanosecond dye laser of high spectral purity with double functional grating

The authors report on a new compact pulsed dye laser cavity arrangement with a U-shaped resonator with an echelle grating and a prism deflecting beam expander with a magnification of 112. The double functional grating is a resonant reflector of the magnified and the non-magnified beam. With this apparatus the broadband background is suppressed leaving up to 0.8% of the small line width signal. The spectral line width of the laser radiation without an intracavity FP etalon is 0.15 cm-1. The line width with a 5 mm air-spaced FP etalon is 0.02 cm-1; and with a 15 mm FP etalon one-mode operation is possible. The passive wavelength stability is better than +or-0.2 pm for 2.5 min or better than +or-1 pm for 3 h. Wavelength tuning is possible by turning the grating and/or the FP etalon or by changing the pressure. The optical energy efficiency when using one amplifier stage is 5% for Rhodamine 6G at 580 nm.

Narrow bandwidth Q-switch alexandrite laser for atmospheric applications

An acousto-optics Q-switch alexandrite laser with a 0.5 pm linewidth is described. The output energy is 20 mJ with a pulse duration of 100 ns (fwhm). A new cavity arrangement is used in which a main non dispersive resonator acting as a forced oscillator is continuously self-injected by a narrow line from an auxiliary cavity. In a separate experiment we report on a (broadband) pulse emission within 100 μs with an equal energy of 50 mJ in each pulse.

Mode selection in standing wave lasers by an induced gain grating

A novel method of overcoming spatial hole burning, in order to achieve narrow-band operation of a standing wave laser, is proposed. Frequency selection is obtained by the interaction between cavity modes and a grating induced in the active medium. A third-order Lamb theory analysis of the proposed system is made and the coefficients for net gain, self, and cross saturation obtained. These coefficients are used to examine the stability of the cavity modes. It is shown that, for the case of a transversely pumped dye laser, single-frequency selection should be possible using a suitable cavity arrangement.

Some Studies on the Effect of the Resonant Cap on the Oscillator Performance ofX-Band Gaas and Si Impatt Oscillators

X'-band GaAs and Si IMPATT oscillators have been developed using a compact heat-sink cum waveguide cavity arrangement with diodes mounted between a resonant cap and the broad face of the waveguide. In the operating current range, tuned maximum power output and the efficiency at a given dc bias current are strongly dependent on the resonant cap diameter which mainly determines the frequency of oscillation. The maximum efficiency of the GaAs IMPATT oscillator was found to be 19% at a power level of 1.4 W when the device optimum frequency nearly corresponds to freq of oscillation determined by the resonant cap. On the other hand, the maximum efficiency considerably degrades with resultant decrease of tuned maximum power output when the oscillating frequency determined by the cap diameter appreciably differs from the frequency of maximum negative conductance of the diode. Similar investigations have been carried out on Si SDR IMPATT oscillators for various sizes of the resonant cap which show that the power output and efficiency peaks at an optimum size of the resonant cap for a given device.