Probe Gain Research Articles

Probe Absorption Spectroscopy As a Tool to Study the Excited States in a Cooperative System of Two Organic Molecules

The applicability of the method for measuring the probe absorption and gain spectra in a system of quantum emitters excited by a resonant driving field for studying cooperative photoluminescence is considered. The gain and attenuation of a probe signal in the system of two quantum emitters with the dipole–dipole interaction have been calculated for the conditions of observing the cooperative photoluminescence of a pair of impurity molecules described in the literature and close to them. The resulting dependences demonstrate the structure of excited collective molecular states, which can be used to reconstruct the positions of molecules in a matrix and to determine the difference in their photophysical properties. Thus, the probe absorption and gain spectra can be used to analyze the photoluminescence of quantum-entangled particles and to transform light signals.

Investigating transfer of coherence, direction of light propagation and Rydberg blockade in a four-level [formula omitted]-type system under linear and nonlinear interaction regimes

This theoretical study reveals that the transfer of coherence (TOC) and the direction of light propagation vector play a crucial role in transitioning from electromagnetically induced transparency (EIT) to electromagnetically induced absorption (EIA) in a four-level closed and open cascade (Ξ)-type light-atom interacting systems (LAIS) under both linear as well as nonlinear interaction regimes. It is found that the amplitudes of the coherence signals are distinctly influenced by the system’s openness driven by the presence of additional dipole allowed levels not connected by the lasers and the type of interaction regimes. The effect of TOC on the EIT to EIA transition is discussed in detail by the velocity-dependent dressed state analysis and velocity mapping of the probe absorption coefficient. The findings also reveal that the efficiency of the counter-propagation scheme of the coupling fields is higher than the co-propagation scheme. Furthermore, we have estimated the Rydberg blockade effect on the probe absorption profiles for some specific velocity groups of atoms, which exhibit probe gain in the medium along with EIT and EIA patterns.

Perfect non-reciprocal reflection amplification in closed loop coherent gain atomic system

High-performance non-reciprocal photonic devices can improve the efficiency of optical quantum manipulation, information processing, and quantum simulation effectively. The enhanced optical signal can simultaneously amplify the weak signal output by the quantum system and isolate the sensitive quantum system from the back-scattered external noise, which is the core technology of high-performance photonic devices. In our previous work (<ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://doi.org/10.1364/OE.499738">2023 <i>Opt. Express</i> <b>31</b> 38228</ext-link>), we have achieved dynamic control of unidirectional reflection amplification based on four-wave mixing gain and the use of coupling field intensity varying linearly with position. In this work, we design a simple three-level closed loop coherent gain atomic system, setting the intensity of coupling field to be varying with position step shape to break the spatial symmetry of probe susceptibility, and achieving perfect non-reciprocal reflection light amplification. In contrast, the stepped variation of coupling field intensity is easier to adjust in experiment, greatly reducing the difficulty in the experiment. Specifically, the system introduces phase modulation. By changing the phase, the frequency region of probe gain and absorption can be switched, which makes the modulation of reflection amplification more flexible.

Acoustical intensity probe based on a polyvinylidene fluoride bimorph.

This study investigates complex acoustical intensity using a polyvinylidene fluoride (PVDF) bimorph. Analytical models of the open-circuit voltage outputs of an infinite-strip-shaped PVDF bimorph cantilever in an underwater sound field are developed. Results show that the sound pressure generates the sum of the outputs, while the particle velocity normal to the PVDF surface generates the difference. The sensitivities of the pressure- and velocity-generated voltage responses with respect to an incident plane sound field demonstrate uniform directivity in a low-frequency range, which is suitable for acoustical intensity determination. The higher velocity sensitivity confirms the advantage of using a PVDF bimorph as a velocity sensor, owing to its light weight and flexibility. An algorithm for determining the complex acoustical intensity normal to the surface is proposed by utilizing those voltage responses and the probe gain calibrated with a given angle of incident sound. This algorithm allows accurate determination of sound intensity of a plane wave field, where the reactive part of intensity is absent. However, a small error may exist when the reactive intensity is large and active intensity is small. This small discrepancy arises from the inherent variation in the phase directivity of the gains, which decrease with frequency.

Effective Control of the Optical Bistability of a Three-Level Quantum Emitter near a Nanostructured Plasmonic Metasurface

We study, theoretically, the phenomena optical bistability and multistability of a hybrid quantum-plasmonic system immersed within an optical ring cavity. The hybrid quantum-plasmonic system consists of a three-level V-type quantum emitter and a two-dimensional plasmonic metasurface of gold nanoshells. The quantum emitter and the plasmonic metasurface are placed in close proximity to each other so that a strong quantum interference of spontaneous emission occurs, which enables the strong modification of optical-bistability/ multistability hysteresis curves. Along with this, the strong interaction between the emitter and the plasmonic metasurface allows for active control of the corresponding bistable threshold intensity. Furthermore, we show that by varying the metasurface-emitter separation, a transition from bistability to multistability of the hybrid system is observed. Lastly, by introducing an additional incoherent pumping in the system, we have the emergence of phenomena, such as probe absorption and gain, with or without population inversion. The results may find technological application in on-chip nanoscale photonic devices, optoelectronics and solid-state quantum information science.

Control of an electromagnetically induced grating by Er3+ ion concentration in an Er3+-doped YAG crystal

We investigate the effect of doped E r 3 + ion concentration on an electromagnetically induced grating in an E r 3 + -doped yttrium aluminum garnet (YAG) crystal. Due to the change of electric dipole moment and spontaneous emission decay induced by E r 3 + ion concentration, the Fraunhofer diffraction of the solid-state grating is sensitively dependent upon E r 3 + ion concentration. The three-level E r 3 + ion system with a closed loop leads to probe gain appearing in some concentrations of the E r 3 + ion, which significantly improves the first-order diffraction efficiency of the solid-state grating. Furthermore, it is demonstrated that the relative phase, signal detuning, and grating thickness have different effects on the first-order diffraction efficiency of the solid-state grating under different concentrations of the E r 3 + ion. Therefore, our scheme may provide a basis for selecting a suitable concentration to realize high-efficiency optical switching and routing in future integrated systems.

Microwave assisted gain in inverted-Y type atomic system

The probe response in four-level inverted-Y configuration showsgainwithout population inversionin presence of microwave field.At on-resonant probe field, switching between superluminal and subluminal probe propagation under the influence of microwave field is discussed in details.Both the bandwidth and sharpness of optical switching can easilybe controlled by varying the microwave power. The switching action improves immensely if the control transition is chosen to be a Rydberg transition. The transient behavior of the atomic system ultimately settles into probe gain under the influence of the microwave field.A way of transferring population to the highest excited state through the application of microwave field is also discussed.

57-64 GHz Imaging/Detection Sensor–Part I: System Setup and Experimental Evaluations

A novel experimental evaluation of millimeter-wave imaging / detection system based on time domain reflectometry (TDR) is presented. The proposed 60 GHz-band system is characterized by high precision, lightweight, low profile, and utilization of low cost scanning probes. As a scanning sensor, multi sin-corrugation antipodal tapered slot antenna (MC-AFTSA-SC) with and without a grooved spherical probe is introduced. Although, the precise mechanical setup is especially designed and optimized to hold the proposed scanning probe antenna, it can handle a wide range of probes. The proposed antenna sensor is experimentally evaluated by integrating it in the proposed imaging / detection system. As a bench-marking process, multiple images for different targets are reconstructed using both the proposed probe and conventional standard gain horn (SGH) antenna. The images are generated using 2D linear scanning platform with a cross range resolution $\delta {x}=\delta {y}=3$ mm achieving a $100\times100$ pixels image. The obtained images indicate a superior performance of the proposed scanning probe over the bigger sized SGH. This paper is split into two parts because of its length: this paper (part I) describes the system setup and experimental evaluation of the probes, while part II will discuss experiments for detecting concealed weapons and threatening materials.

One- and two-dimensional electromagnetically induced gratings in an Er3+ - doped yttrium aluminum garnet crystal

A coherently prepared Er3+-doped yttrium aluminum garnet (YAG) crystal with a four-level ionic configuration is exploited for realizing one-dimensional (1D) and two-dimensional (2D) electromagnetically induced gratings (EIGs). Owing to the probe gain induced by the incoherent pump, the diffraction efficiency of the crystal grating, especially the first-order diffraction, can be significantly improved via increasing the incoherent pumping rate or decreasing the probe detuning. The enhancement of the grating diffraction efficiency originates from the interference between the gain and phase gratings. It is also demonstrated that the diffraction of the crystal grating can be dynamically controlled via tuning the intensity and detuning of the standing-wave driving field or the concentration of Er3+ ion. More importantly, the probe energy of the diffraction side lobes around the central principle maximum is comparable to that of the first-order diffraction field for small driving intensity or large driving detuning. Our scheme may provide a possibility for the active all-optical control of optical switching, routing and storage in fiber communication wavelengths.

A Statistical Evaluation of Detection Response of an Electric Field Probe Loaded With Nonlinear Diodes for Modulated Signals

To improve the calibration uncertainty of an electric field probe loaded with diodes to modulated signals, an approximate method for evaluating the detection response using the probability density function (pdf) of the envelope amplitude of an actually transmitted modulated signal waveform is proposed. In this article, we focus on the high-strength modulated signals and evaluate the effect of the nonlinearity of the transmission system on the probe gain. First, the equivalent circuit parameters of an electric field probe are estimated using an unmodulated signal and then used to simulate the probe gain for the amplitude-modulation (AM) signal. The probe gain for the modulated signal deviates considerably from that for the unmodulated signal, depending on the modulating frequency and modulation index of the AM signal, especially when a large incident voltage is applied to the equivalent circuit simulating the probe. Moreover, we propose two approximate expressions using the pdf to obtain the fluctuation range of the detection response of the modulated signal. One is an approximate expression that considers the equivalent circuit parameters of the probe. The other one is an approximate expression for the modulated signal with slow envelope variation. These two expressions are found to give a good approximation of the asymptotic value of the probe gain for an AM signal with fast and slow envelope variations, respectively. By applying these approximate expressions, the upper and lower limits of the gain variation of the probe for the AM signal are obtained. As an application to actual communication signals, integrated services digital broadcasting terrestrial (ISDB-T) signals and single-carrier frequency-division multiple access (SC-FDMA) signals are demonstrated as examples. It is shown that the probe gain in the saturation region increases as the signal bandwidth or peak-to-average-power ratio (PAPR) increases, which can be understood similar to the probe response to AM signals.

Pulse coding linearization for Brillouin optical time-domain analysis sensors.

We introduce a simple method to extend the performance of pulse coding techniques in their application to Brillouin optical time-domain analysis sensors (BOTDA). It is based on applying a simple logarithmic processing on the detected probe wave that compensates the deviation from linearity of the sensor response for long code lengths. The technique ensures that the accumulated effect of a sequence of pulses is equal to the linear addition of the effects of the individual components, which is the essential condition to ensure a correct decoding of the probe gain measurement. We experimentally demonstrate the compensation of the Brillouin frequency shift error induced by the accumulated gain nonlinearity. Furthermore, a proof-of-concept 80km sensing link within a total 200km fiber loop demonstrated a better than 2MHz precision with 2m spatial resolution.

High-precision three-dimensional atom localization in a three-level pump–probe atomic system

We propose a new scheme for three-dimensional (3D) atom localization controlled by incoherent pump in a three-level Λ-type atomic system. The spatial position information of an atom in 3D space can be achieved via measuring probe gain and absorption when the atom passes through three mutually perpendicular standing-wave fields. It is found that high-detecting-probability and high-precision 3D atom localization can be obtained via properly adjusting the relevant parameters in the presence of the combination of a traveling-wave field and three orthogonal standing-wave fields. Furthermore, it is also shown that the incoherent pumping field can switch the localization patterns from the probe-gain sphere to the probe-absorption sphere and enhance 3D atom-localization precision.

Coherent control of three-dimensional atom localization based on different coupled mechanisms

We present a new scheme for three-dimensional (3D) atom localization in a four-level atomic system based on different coupled mechanisms. Owing to the space-dependent atom---field interaction, the position probability distribution of the atom can be directly determined by measuring the probe absorption and gain spectra. It is found that, based on different coupled mechanisms, the probability of finding the atom in 3D space is increased from 25% to 100%. Our scheme may be helpful in optical microscopy, the atom nano-lithography, and measurement of the center-of-mass wave function of moving atoms, etc.

Probe gain via four-wave mixing based on spontaneously generated coherence**Project supported by the Natural Science Foundation of Hainan Province, China (Grant Nos. 20151005, 20151015, and 20161006), the National Natural Science Foundation of China (Grant Nos. 11247005, 51262007, 11501153, and 41564006), the Postdoctoral Scientific Research Program of Jilin Province, China (Grant No. RB201330), the Project Sponsored by Science Research Foundation for

We have studied the probe gain via a double-Λ atomic system with a pair of closely lying lower levels in the presence of two probe and two coherent pump fields. The inversionless gain can be realized by using nondegenerate four-wave mixing under the condition of spontaneously generated coherence (SGC) owing to near-degenerate lower levels. Note that by using SGC, two probe fields can be amplified with more remarkable amplitudes, and the gain spectra of an extremely narrow linewidth can be obtained. Last but not least, our results show that the probe gain is quite sensitive to relative phases due to the SGC presence which allows one to modulate the gain spectra periodically by phase modulation, and can also be influenced by all laser field intensities and frequencies, and the angles between dipole elements.

Two-wavelength pump-probe technique using single distributed feedback laser array to probe gain recovery of an erbium-doped fiber amplifier

Abstract We propose a two-wavelength pump-probe technique to probe the gain recovery characteristics of an erbium-doped fiber amplifier. The two-wavelength pulse pairs are generated through the direct modulation of a single distributed feedback laser array. The proposed technique allows us to measure the wavelength dependence of the recovery time after gain saturation is induced by a signal of the same wavelength.

Heterodyne slope-assisted Brillouin optical time-domain analysis for dynamic strain measurements

We propose a slope-assisted Brillouin sensing scheme based on the interaction between a phase modulated probe and a pulsed pump. The modulation frequency of the probe is chosen so that both first-order modulation sidebands lie within the Brillouin gain spectrum generated by the pump field. Owing to stimulated Brillouin scattering (SBS), a phase modulation to intensity modulation conversion occurs in the probe field upon interaction with the pump, producing a beat note whose amplitude grows with detuning from the SBS resonance. We show that the ratio between the amplitude of the heterodyne signal and the direct component of the probe gain provides a means for performing pump-power independent dynamic strain measurements, therefore improving the conventional slope-assisted brillouin optical time-domain analysis.

Large Kerr index with amplification in an open four-level atomic system with twofold lower levels.

This paper presents a new freedom, which is the result of atomic injection and exit rates from a cavity associated with an open system, thus leading to a remarkable giant Kerr nonlinearity with applications in all-optical switching. The influence of atomic injection and exit rate from the cavity on nonlinear susceptibility of an open four-level Λ-type atomic system with twofold lower levels is investigated. It is found that large Kerr nonlinearity accompanied with probe gain can be obtained by adjusting the atomic injection rates and exit rate from the cavity, which is completely different from those presented in previous closed atomic systems. Phase control of Kerr nonlinearity in such an open atomic system is then studied.

The gain amplification via spontaneously generated coherence with incoherent pump field: A comparison of optical properties between open and closed four level systems

We studied the steady state and transient evolution of probe absorption and population in an open four level N-type atomic system and compared its transient and steady state properties with the corresponding closed system. The effects of incoherent pump field, spontaneously generated coherence, probe detuning and cavity parameters (i.e. the atomic exit rate from cavity and atomic injection rates) on transient and steady state response of probe field and lasing with and without inversion are investigated. It is realized that in an open N-type system, regardless of incoherent pump field applied or not, due to existence of cavity parameter, by adjusting the values of other parameters, we can always obtain lasing without inversion, while there is no gain in closed system without incoherent pump field. Also results are shown that, the probe gain can be greatly amplified with SGC at the presence of incoherent pump field and absence of population inversion. We found that in the same condition the open system is favorable scheme for lasing without inversion.

Pump-probe optical response of an asymmetric double quantum dot molecule

We study the interaction of an asymmetric double semiconductor quantum dot molecule with a weak probe field and a strong pump field. We show that the optical properties of the system are controlled by a gate voltage and the pump field. For example, we find that the application of the pump field leads to controlled probe absorption, optical transparency, and gain for weak tunneling rates, while for stronger tunneling rates optical gain disappears and absorption spectra with double peaks are formed.

Controlling of Goos-Hänchen shift via biexciton coherence in a quantum dot

Controlling of the Goos-Hanchen (GH) shifts of the reflected and transmitted probe pulses through a cavity containing four-level GaAs/AlGaAs quantum dot with 15 periods of 17.5 nm GaAs wells and 25-nm Al0.3Ga0.7As barriers is investigated. Under appropriate conditions, the probe absorption can be converted to the probe gain, therefore, the controlling of negative and positive GH shift in the both reflected and transmitted probe beams can be occurred simultaneously. Our obtained results show that the group index of the probe beams could be negative or positive in both reflected and transmitted pulses. Therefore, simultaneous subluminal or superluminal light propagation in reflected and transmitted pulses can be achieved.