Showing papers on "Signal beam published in 2015"

Optical parametric amplification via non-Hermitian phase matching

Abstract: We introduce the notion of dissipative optical parametric amplifiers (DOPA) and demonstrate that, even in the absence of the Hermitian phase-matching condition in these structures, the signal beam can be amplified when the idler mode suffers optical attenuation. We discuss the optical implementation of this concept in waveguide platforms, and we propose different methods to control the optical loss of these configurations only at the wavelength of the idler component. Surprisingly, this spectrally selective dissipation process allows the signal beam to draw more energy from the pump and, as a result, attains net amplification. Similar results also apply if the losses are introduced only to the signal component. This intriguing feature can open new avenues for building long wavelength light sources and parametric amplifiers by using semiconductor planar structures, where Hermitian phase-matching requirements can be difficult to satisfy without adding stringent geometric constraints or relatively complex fabrication steps.

Electric field measurements in a dielectric barrier nanosecond pulse discharge with sub-nanosecond time resolution

Abstract: The paper presents the results of time-resolved electric field measurements in a nanosecond discharge between two plane electrodes covered by dielectric plates, using picosecond four-wave mixing diagnostics. For absolute calibration, the IR signal was measured in hydrogen at a pressure of 440 Torr, for electrostatic electric field ranging from 0 to 8 kV cm−1. The calibration curve (i.e. the square root of IR signal intensity versus electric field) was shown to be linear. By measuring the intensities of the pump, Stokes, and IR signal beam for each laser shot during the time sweep across the high-voltage pulse, temporal evolution of the electric field in the nanosecond pulse discharge was determined with sub-nanosecond time resolution. The results are compared to kinetic modeling predictions, showing good agreement, including non-zero electric field offset before the main high voltage pulse, breakdown moment, and reduction of electric field in the plasma after breakdown. The difference between the experimental results and model predictions is likely due to non-1D structure of the discharge. Comparison with the kinetic modeling predictions shows that electric field in the nanosecond pulse discharge is controlled primarily by electron impact excitation and charge accumulation on the dielectric surfaces.

Wavelength modulation spectroscopy with signal–reference beam method for highly sensitive gas detection

Abstract: Wavelength modulation spectroscopy combined with signal–reference beam method is used for trace gas detection. The developed technique combines the advantages of common-mode noise suppression and signal-to-noise ratio improvement. The performance of the resulting water vapor sensor is markedly improved because of scanning baseline suppression, effective suppression of the target gas content in the components and resistance to external factors such as temperature and humidity. Trace water vapor detection experiments verify that the measurement accuracy of the system can reach 1 ppmv for an optical path length of 10 cm.

Polarization singularities in a sum-frequency light beam generated by a bichromatic singular beam in the bulk of an isotropic nonlinear chiral medium

Abstract: Expressions for the electric field at a sum frequency generated by a collinear elliptically polarized Gaussian beam and circularly polarized Laguerre-Gaussian beam in an isotropic chiral nonlinear medium are obtained in quadratures. The amount and locations of $C$ points in the cross section of a signal beam at a sum frequency are shown to be dependent on frequency and diffraction lengths ratios of fundamental beams and on the ellipticity degree of the Gaussian beam's polarization ellipse. Possible values of total topological charges of the emergent $C$ points are determined by the topological charge of the Laguerre-Gaussian beam and remain constant while the radiation propagates in nonlinear media. In case of nonzero total topological charge $C$ lines form helical structures, the parameters of which depend on the wave-vector mismatch. Otherwise, $C$ lines form a loop. As the wave-vector mismatch grows the loop undergoes deformation and breaks up, creating new $C$ lines.

Closed loop tracking system using signal beam

Abstract: The invention is a system and method for heliostat mirror control. Here, each heliostat mirror generates a low intensity “signal beam”, directed at an angle off from the heliostat mirror's high intensity and sensor blinding “main beam” of reflected solar energy. The low intensity signal beams may be created by reflecting a small portion of the incident solar light at an angle from the main beam, by reflected artificial light, or from lasers shinning onto mirrors from known locations. The signal beams are detected by optical sensors mounted way from the main heliostat receiver focus, and can be used in a closed loop control system to efficiently ensure that individual heliostat mirrors in a heliostat array accurately track sunlight and direct the sunlight to a central receiver. Because heliostat mirrors need not be taken “off sun” for positioning, the system allows heliostat arrays to be run at high efficiency.

Theoretical and experimental investigations on measuring underwater temperature by the coherent Brillouin scattering method.

Abstract: In this paper, a new method of measuring a water-stimulated Brillouin scattering (SBS) frequency shift by optical coherent detection is presented, in order to remote-sense the underwater temperature of the ocean. A single longitudinal mode, passively Q-switched pulsed Nd:YAG laser is used as the light source, the water SBS beam is used as the signal beam, and a portion of the incident laser beam is used as the local oscillator. The heterodyne is detected by a high-speed photodetector, and the heterodyne frequency is the Brillouin frequency shift. Therefore, the underwater temperature can be determined according to the relationship between the Brillouin frequency shift and the water temperature. To test and verify its practicability, the heterodyne waveforms at different water temperatures are recorded in the laboratory with a wide-band oscilloscope, and the Brillouin frequency shifts are deduced by a Fourier transform. The experimental results are consistent with the theoretical analysis. This work provides the foundation for the development of a water temperature measurement system based on coherent Brillouin scattering.

Imaging of transient surface acoustic waves by full-field photorefractive interferometry

Abstract: A stroboscopic full-field imaging technique based on photorefractive interferometry for the visualization of rapidly changing surface displacement fields by using of a standard charge-coupled device (CCD) camera is presented. The photorefractive buildup of the space charge field during and after probe laser pulses is simulated numerically. The resulting anisotropic diffraction upon the refractive index grating and the interference between the polarization-rotated diffracted reference beam and the transmitted signal beam are modeled theoretically. The method is experimentally demonstrated by full-field imaging of the propagation of photoacoustically generated surface acoustic waves with a temporal resolution of nanoseconds. The surface acoustic wave propagation in a 23 mm × 17 mm area on an aluminum plate was visualized with 520 × 696 pixels of the CCD sensor, yielding a spatial resolution of 33 μm. The short pulse duration (8 ns) of the probe laser yields the capability of imaging SAWs with frequencies up to 60 MHz.

Optical image measuring apparatus

Abstract: A clear image of a measurement target in optical coherence tomography (OCT) is obtained while suppressing influence of reflected light from a specific portion Included are a laser beam source, a beam splitter that splits a laser beam into a signal beam and reference beam; an objective lens that focuses the signal beam onto a measurement target in a container, a unit that moves the signal beam focus position, an objective lens that focuses the reference beam, a reflecting mirror, a flat plate arranged between the objective lens and reflecting mirror, and interference optics that combine the signal beam reflected by the measurement target with the reference beam reflected by the reflecting mirror and having passed through the objective lens Three or more interference beams with different phases, and photodetectors that detect the interference beams are generated, and two of the objective lenses are the same lenses

Hologram recording apparatus and method for recording holographic element images using spatial light modulator (slm)

Abstract: Provided is an apparatus and method for recording holographic element images using a spatial light modulator (SLM), the apparatus including a recording light source unit to split a source beam output from a light source into a first output beam and a second output beam and output the first output beam and the second output beam, a reference beam generator to eliminate a distortion of the first output beam, and generate a reference beam by controlling a size and a shape of the distortion-eliminated first output beam, an object beam generator to generate an object beam by eliminating a distortion of the second output beam, and an object beam converging lens system to output a signal beam by modulating an object beam using a holographic element image, split the output signal beam in a plurality of directions, and converge split signal beams to be incident to a hologram film

Surgical Microscopes Using Optical Coherence Tomography and Related Systems

Abstract: Some embodiments of the present inventive concept provide optical coherence tomography (OCT) systems for integration with a microscope. The OCT system includes a sample arm coupled to the imaging path of a microscope. The sample arm includes an input beam zoom assembly including at least two movable lenses configured to provide shape control for an OCT signal beam; a scan assembly including at least one scanning mirror and configured for telecentric scanning of the OCT signal beam; and a beam expander configured to set the OCT signal beam diameter incident on the microscope objective. The shape control includes separable controls for numerical aperture and focal position of the imaged OCT beam.

Nonlinear Negative Refraction by Difference Frequency Generation

Abstract: Negative refraction has attracted much interest for its promising capability in imaging applications. Such an effect can be implemented by negative index meta-materials, however, which are usually accompanied by high loss and demanding fabrication processes. Recently, alternative nonlinear approaches like phase conjugation and four wave mixing have shown advantages of low-loss and easy-to-implement, but associated problems like narrow accepting angles can still halt their practical applications. Here we demonstrate theoretically and experimentally a new scheme to realize negative refraction by nonlinear difference frequency generation with wide tunability, where a thin BBO slice serves as a negative refraction layer bending the input signal beam to the idler beam at a negative angle. Furthermore, we realize optical focusing effect using such nonlinear negative refraction, which may enable many potential applications in imaging science.

Triple detection fiber differentiating interferometer based on low-coherence interferometer and its passive demodulation scheme

Abstract: This paper presents a triple detection fiber differential interferometer and its passive demodulation scheme. The interferometer is based on an all fiber Mach–Zehnder and Sagnac hybrid configuration, which is composed of a fiber ASE source, a section of delay fiber, a 3×3 fiber coupler and several other fiber components. In the interferometer, the signal beam and reference beam travel along the same path but in opposite directions. The received signal is demodulated by a triple detection passive demodulation scheme. The interferometer can measure the absolute amplitudes and frequencies of phase sensitive signals with large dynamic range, and the low frequency environmental disturbance is removed simultaneously due to the phase compression mechanism. The experimental results demonstrate that the phase demodulation resolution is 6×10 −5 rad and the maximum measuring amplitude is up to 90 rad. This method can be used to measure many kinds of parameters such as vibration and refractive index.

Free space 90-degree optical mixer

Abstract: The invention relates to a free space 90-degree optical mixer, which comprises a beam combining unit, an in-phase balance receiving channel, an orthogonal balance receiving channel and a receiving unit, wherein the combining unit combines a signal beam and a local oscillator beam, the in-phase balance receiving channel generates 0-degree and 180-degree relative phase shift combination beams, the orthogonal balance receiving channel generates 90-degree and 270-degree relative phase shift combination beams, and the receiving unit receives the 0-degree, 90-degree, 180-degree and 270-degree relative phase shift combination beams. The free space 90-degree optical mixer provided by the invention improves the accuracy and is convenient to adjust and install.

Analysis of counting measurements on narrowband frequency up-converted single photons and the influence of heralding detector dead time

Abstract: We present a theoretical model of photon counting measurements on conditionally generated narrowband single-photon states that are produced via cavity-enhanced spontaneous parametric down-conversion, then frequency up-converted from the telecom wavelength of 1550 nm to the visible wavelength of 532 nm. The highly nonclassical character of the up-converted states is certified by a quantum non-Gaussianity witness that is determined from coincidence measurements with single-photon detectors in a Hanbury-Brown--Twiss configuration. We find our model in good agreement with the experimental data, and we investigate a useful effect caused by the dead time of the trigger detector, whose clicks herald conditional preparation of the single-photon state. Due to the dead time, a click of the trigger detector excludes the possibility of a trigger event at a certain preceding time interval, during which the measured idler beam is thus projected onto a vacuum state. Due to quantum correlations between signal and idler beams, this reduces the multiphoton contributions in the conditionally generated state of the signal beam and accordingly increases the value of the quantum non-Gaussianity witness. We also show that spurious heralding detections due to after-pulsing can be suppressed by accepting a click of the trigger detector only if its distance from a previous click of this detector exceeds a certain suitably chosen threshold.

Rotation spacing and multiplexing number in angle-peristrophic multiplexing holographic memory

Abstract: Holographic memory is expected to be the next-generation optical memory with several advantages including high data transfer rate and high recording density Holographic memory enables the storage of holograms in the same location in a holographic medium typically using the angle multiplexing method The multiplexing number is an important factor that determines the recording density when using this method To increase the multiplexing number, it is known as an effective method to combine peristrophic (or rotation) multiplexing with angle multiplexing We use the k-sphere to describe that the rotation spacing for peristrophic multiplexing depends on both the numerical aperture in the signal beam path and the angle between the reference and signal beams We then formulate the rotation spacing and compare the results obtained using the theoretical formula with the measured results Finally, we estimate the maximum multiplexing number for our experimental system using the angle-peristrophic multiplexing method on the basis of the measured results

Interference coordination method and base station

Abstract: Provided are an interference coordination method and a base station. The method comprises the following steps: receiving, by a base station, an interference coordination request sent by a neighbouring cell base station, wherein the interference coordination request is sent by the neighbouring cell base station after determining a signal beam to be coordinated from various signal beams transmitted by itself (301); acquiring, by the base station, silence region information about a silence region to be coordinated corresponding to the signal beam to be coordinated according to the interference coordination request, wherein a signal beam in the silence region to be coordinated would cause interference to the signal beam to be coordinated (302); and not transmitting, by the base station, the signal beam in the silence region (303). By means of the present invention, mutual interference between signal beams of various neighbouring base stations can be effectively avoided.

High-power all-fiber MOPA structure superfluorescence fiber light source based on tandem pumping

Abstract: The invention discloses a high-power all-fiber MOPA structure superfluorescence fiber light source based on tandem pumping. The high-power all-fiber MOPA structure superfluorescence fiber light source comprises a superfluorescence seed light source, a power preamplifier and a tandem pumping power main amplifier, wherein the superfluorescence seed light source comprises a first residual pumping light decanter, a first side pump beam combiner, a first multimode pumping laser, a first double-clad ytterbium-doped fiber, a second side pump beam combiner, a second residual pumping light decanter, a first fiber isolator and a second fiber isolator; the power preamplifier comprises a first (N+1)*1 fiber pumping signal beam combiner, a second multimode pumping laser, a second double-clad ytterbium-doped fiber, a second residual pumping light decanter and a third fiber isolator; and the tandem pumping power main amplifier comprises a second (N+1)*1 fiber pumping signal beam combiner, a tandem pumping laser module, a third double-clad ytterbium-doped fiber, a third (N+1)*1 backward pumping signal beam combiner, a fourth residual pumping light decanter and a fiber output end cap. The high-power all-fiber MOPA structure superfluorescence fiber light source based on the tandem pumping realizes output of a high-brightness superfluorescence fiber light source.

Optical and Quasi-Optical Analysis of System Components for a Far- Infrared Space Interferometer

Abstract: Many important astrophysical processes occur at wavelengths that fall within the far-infrared band of the EM spectrum, and over distance scales that require sub-arc second spatial resolution. It is clear that in order to achieve sub-arc second resolution at these relatively long wavelengths (compared to optical/near-IR), which are strongly absorbed by the atmosphere, a space-based far-IR interferometer will be required. We present analysis of the optical system for a proposed spatial-spectral interferometer, discussing the challenges that arise when designing such a system and the simulation techniques employed that aim to resolve these issues. Many of these specific challenges relate to combining the beams from multiple telescopes where the wavelengths involved are relatively short (compared to radio interferometry), meaning that care must be taken with mirror surface quality, where surface form errors not only present potential degradation of the single system beams, but also serve to reduce fringe visibility when multiple telescope beams are combined. Also, the long baselines required for sub-arc second resolution present challenges when considering propagation of the relatively long wavelengths of the signal beam, where beam divergence becomes significant if the beam demagnification of the telescopes is not carefully considered. Furthermore, detection of the extremely weak far-IR signals demands ultra-sensitive detectors and instruments capable of operating at maximum efficiency. Thus, as will be shown, care must be taken when designing each component of such a complex quasioptical system.

Tuning characteristics of femtosecond optical parametric oscillator with broadband chirped mirrors

Abstract: We present the investigation of a synchronously pumped optical parametric oscillator (SPOPO) based on beta barium borate (BBO) nonlinear crystal with broadband complementary chirped mirror pairs (CMPs). Three SPOPO cavity configurations with slightly different intracavity dispersion were explored. Dispersion properties of cavity mirrors were characterized using a white light interferometer and found to be the key factor determining the gap-free tuning range as well as simultaneous multiwavelength generation. The SPOPO is pumped by the second harmonic of a Yb:KGW oscillator and provides signal pulses tunable over a spectral range from 625 to 980 nm. Signal pulse duration ranges from 102 to 268 fs in various intracavity dispersion regimes. In addition, signal beam power in excess of 500 mW is demonstrated, corresponding to 27% conversion efficiency from pump to signal wave.

Transverse shearing interferometer based 90-degree optical mixer

Abstract: The invention relates to a transverse shearing interferometer based 90-degree optical mixer, which comprises a beam combining unit, balance receiving channels and a receiving unit, wherein the beam combining unit combines a signal beam and a local oscillator beam, the balance receiving channels generate 0-degree, 90-degree, 180-degree and 270-degree relative phase shift combination beams, and the receiving unit receives the 0-degree, 90-degree, 180-degree and 270-degree relative phase shift combination beams The transverse shearing interferometer based 90-degree optical mixer provided by the invention is high in precision and convenient to adjust and install

Device and method for improving wavefront quality of atmosphere laser communication link

Abstract: The invention provides device and method for improving wavefront quality of an atmosphere laser communication link. The device comprises a collimating eyepiece at the ground receiving end; a first half-wave plate and a first polarization beam splitter are sequentially arranged in the signal beam output direction of the collimating eyepiece; a second polarization beam splitter, a second half-wave plate, an optical 4f system, a third polarization beam splitter, a single-die fiber coupler and a single-die fiber are sequentially arranged in the reflecting light direction of the first polarization beam splitter; a first 1/4 wave plate and a quick reflector are sequentially arranged at the right of the second polarization beam splitter; a second 1/4 wave plate and a deformation mirror are sequentially arranged at the left of the second polarization beam splitter; a hartmann wavefront sensor is arranged at the left of the third polarization beam splitter; the output end of the hartmann wavefront sensor is connected with a computer; the output end of the computer is connected with the control ends of the quick reflector and the deformation mirror. According to the device, the wavefornt deformation of a signal beam can be corrected on real time, thus the wavefront quality and the coupling efficiency of the single-die fiber are increased, and meanwhile, the band width and height compensation precision of the system is increased.

Anti-interference quantum imaging apparatus and method of weakly absorbed target by sub shot noises

Abstract: The invention discloses an anti-interference quantum imaging apparatus and method of a weakly absorbed target by sub shot noises. According to the main thinking, a laser 1 generates a laser pulse and the laser pulse passes through a telescope 2, a half wave plate 3, a BBO crystal 4 successively to generate a signal beam and an idle beam; the idle beam passes through a high-pass totally-reflecting mirror 5, a lens 6, a first orthogonal polarization selection plate 7 and a narrow-band filtering plate 9 to obtain a useful signal beam passing through the narrow-band filtering plate 9; and the idle beam passes through the high-pass totally-reflecting mirror 5, the lens 6, a second orthogonal polarization selection plate 8 and a narrow-band filter mirror 10 to obtain a useful idle beam passing through the narrow-band filter mirror 10. A charge coupling device 12 detects the useful signal beam passing through a to-be-image target 11 and the useful idle beam passing through the narrow-band filter mirror 10 respectively to obtain an effective signal beam and an effective idle beam; and a signal processing module 13 obtains an quantum imaging result of the to-be-image target 11 according to the effective signal beam and the effective idle beam.

Optical characteristic measuring apparatus using interrogation optical fiber, optical fiber sensor system having the same, and optical characteristic measuring method

Abstract: The disclosure relates to an optical characteristic measurement system including at least: a light source unit which outputs an input beam of a specific wavelength; a sensing unit which generates a signal beam by using a sensor whose optical characteristic is affected by an external environment condition; and a measuring unit which derives varied physical amount by using the signal beam delivered from the sensing unit, wherein the measuring unit includes: an optical coupler which distributes the signal beam into the two optical paths; and an interrogation optical fiber which is arranged on one of the paths on which the signal beam travels. The interrogation optical fiber has a linear light absorption characteristic in the specific wavelength range, and the light intensity of the signal beam is measured to detect a wavelength of the signal beam delivered from the sensing unit, and finally derive the physical amount applied from outside.

Multi Mode Stimulated Emission Depletion Microscope System Combined with Digital Holography Method

Abstract: This microscope system is published using wavelength beam and the STED beam Microscope system 100 according to an embodiment of the present invention, the excitation wavelength beam (Excitation Beam) generator 111 and a STED beam (Stimulated Emission Depletion Beam) generating a beam generating unit (110) comprising a device (112); Here, focusing on wavelength beam-generating apparatus after the excitation wavelength of the beam generated from the 111 through the DM (Dichroic Mirror, 121) the measuring object (10) and at the same time, a STED beam generated from the STED beam generating unit (112) of; (phase mask, 122 PM) and DM (Dichroic Mirror, 123), the measurement object 10 in the focusing (focusing) on ​​the measuring object (10) after having passed by the fluorescence emission, the measuring object 10, a phase mask, STED (Stimulated Emission Depletion) microscope section 120 for acquiring image information; Then generated from the STED beam generating unit 112 is divided by the STED beam out of the absorption wavelength of the fluorophore into two paths using a BS (Beam Splitter, 131), one path is a reference beam (Reference Beam) Sensor ( headed to 132), and the other path is the signal beam (signal beam) as directed to the measuring object 10, and transmits the measurement object (10) for obtaining holographic information on the basis of the signal beam and the reference beam of the modulated light path occurred digital holographic (digital holographic) microscope section 130; And arithmetic to restore the image information of the STED microscope section 120 and the digital alone measured on the basis of image information and the hologram information of the subject acquired through the graphical microscope section 130 Target 10 and calculates the quantitative phase information and in that it comprises a base in the configuration; processor 140

Switchable multi perspective detector, optics for switchable multi perspective detector, and method of operating switchable multi perspective detector

Abstract: PROBLEM TO BE SOLVED: To improve detection of a signal beam by a secondary charged particle detection device specifically used in a scanning electron microscope.SOLUTION: A secondary charged particle detection device for detecting a signal beam includes: a detector structure (220) having at least two detection elements (222) with active detection areas, the detection elements being separated from each other; and a particle optics (200) configured for separating the signal beam into a first portion and at least one second portion, and also configured for focusing the first portion and the at least one second portion. The particle optics includes: an aperture plate (201); and at least a first aperture opening (202) provided in the aperture plate, and at least one second aperture opening (204) provided in the aperture plate. The first aperture opening has a concave shaped portion, and particularly the first aperture opening has a pincushion shape.

Dynamical anisotropy of the optical propagation paths

Abstract: Dynamics of laser beam intensity profile spatial modulations over a model tropospheric path with the controlled meteorological parameters was studied Influence of the underlying surface temperature as well as the side wind load were considered The increase of dynamic anisotropic disturbances saturation with the path length was observed Spatio-temporal correlation characteristics of the directivity pattern in the signal beam registration plane were obtained Proposed method of the experimental samples analysis on the base of chronogram with the following definition of the dynamic structure tensors array allows to estimate local and averaged projections of the flow velocities over the chosen spatio-temporal region and to restore their geometry in the zone of intersection with the signal beam Additional characteristics suggested for the diagonalized local structure tensors such as local energy capacity and local structuredness are informative for the estimation of the inhomogeneities spatial dimensions, time of access through the section considered, the dynamics of energetic jets The concepts of rotational and translational dynamic anisotropy are introduced to discriminate the types of the changes of the local ellipsoids axes orientation as well as their values Rotational anisotropy shows itself in the changes of the local ellipsoids orientation, thus characterizing the illumination variation over the beam cross-section Translational anisotropy describes the difference between the axes values for local ellipsoids

Measuring device and measuring method

Abstract: An objective of the present invention is to provide a measuring device for which the need for adjustment of a coherence optical assembly when changing a molecule to be measured is eliminated. A measuring device (1) comprises: a light source unit (10) which emits a pump beam (PP), a Stokes beam (ST), and a signal beam (SG); a light projection unit (20) which projects the pump beam (PP) and the Stokes beam (ST) upon a subject (S); a light modulation unit (30) which modulates the wavelength of the signal beam (SG); a first light detection unit (50) which detects coherent light between the wavelength-modulated signal beam (SG) and an anti-Stokes beam (AS) from the subject (S); a second light detection unit (52) which detects coherent light between the signal beam (SG) and the wavelength-modulated signal beam (SG); and a signal detection unit (60) which detects, from the signal from the first light detection unit (50), a component which is 90° out of phase with the signal from the second light detection unit (52). An optical parametric oscillator (12) of the light source unit (10) further comprises two nonlinear optical crystals which rotate to incline at the same angle in opposite directions with respect to the optical path.

Nanosecond high-pulse energy 1.57 μm KTA optical parametric amplifier with time delay

Abstract: An efficient two-stage KTiOAO4 optical parametric amplifier (OPA) system with walk-off-compensating alignment is designed. By introducing an extra time delay between the pump pulse and the signal pulse, this OPA architecture is capable of obtaining high optical conversion efficiency and high signal gain simultaneously. Finally, a maximum gain of 98 at the 1.57 μm wavelength is obtained with the signal beam quality of M2 around 5.6. The efficiency of the optical conversion from 1.064 to 1.57 μm is around 26%.

Slow light and narrow resonances in electromagnetic-induced deflection

Abstract: A signal beam is generated in three and four level-atomic system in hot Rb vapors with N 2 buffer in electromagnetically induced transparency (EIT) conditions by adding a pump-beam deflected within a small angle to the coupling and probe beams. Linewidth below 200 Hz and time delay above 1 msec are reported. It is suggested that the generated signal proprieties offer several advantages over the transmitted ones that are used traditionally in EIT applications.