This PDF file contains the front matter associated with SPIE Proceedings Volume 8998, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.
The slow light technology prompts the realization of the all-optical storage, by which one can store the information of different wavelengths at their corresponding locations. The induction of plasmon induced transparency (PIT) provides a reliable and easy implement way to achieve slow light transmission and optical storage on the nanometer scale. Meanwhile, the linewidth and position of the PIT can be adjusted by changing the parameters of materials and structures, rather than just depend on the atom level itself in Electromagnetically induced transparency (EIT). More importantly, it can also be integrated with semiconductor devices on the chip, which is an exciting expectation for optoelectronic integration. PIT technology can pave a new way to optical information processing.
This study presents numerical simulations of the maximum sensitivity to absolute rotation of a number of coupled resonator optical waveguide (CROW) gyroscopes consisting of a linear array of coupled ring resonators. It examines in particular the impact on the maximum sensitivity of the number of rings, of the relative spatial orientation of the rings (folded and unfolded), of various sequences of coupling ratios between the rings and various sequences of ring dimensions, and of the number of input/output waveguides (one or two) used to inject and collect the light. In all configurations the sensitivity is maximized by proper selection of the coupling ratio(s) and phase bias, and compared to the maximum sensitivity of a resonant waveguide optical gyroscope (RWOG) utilizing a single ring-resonator waveguide with the same radius and loss as each ring in the CROW. Simulations show that although some configurations are more sensitive than others, in spite of numerous claims to the contrary made in the literature, in all configurations the maximum sensitivity is independent of the number of rings, and does not exceed the maximum sensitivity of an RWOG. There are no sensitivity benefits to utilizing any of these linear CROWs for absolute rotation sensing. For equal total footprint, an RWOG is √N times more sensitive, and it is easier to fabricate and stabilize.
Slow and stopped light systems form an important piece of the photonics puzzle by acting as memory devices. When used with few-photon light levels, these devices are fundamental to applications in quantum information science, quantum computing, and quantum communication. We report on our progress implementing a technique 1 for measuring the quantum state of light that has been stored in a warm-vapor slow-light system. This technique does not require careful mode matching can in fact be used to optimize the measured eld mode without a prior knowledge of the stored light.
Due to its vital role in many quantum information and communication protocols, much theoretical and experi- mental work has been conducted in order to investigate the fundamental properties of entanglement. In this work we describe an experimental investigation into the behavior of continuous-variable entanglement and quantum mutual information upon propagation through slow- and fast-light media. A four-wave mixing process in warm atomic vapor is used to generate an entangled two-mode squeezed vacuum state of light. One of the two modes of the resulting state is then sent through a second four-wave mixing process that is tuned to exhibit either slow- or fast-light properties. The cross-correlation and quantum mutual information shared between the resulting modes is quanti ed, and di erences in their behavior after propagation through slow- and fast-light media are discussed.
Using atomic motion to coherently spread light information stored in atoms provides a novel means to manipulate atom-light interactions. We demonstrate light splitting with moving atoms in a paraffin coated vapor cell, by using phase sensitive degenerate four wave mixing, or self-rotation. This scheme amplifies the beam splitter signal, and in the meantime maintains the phase coherence between the beam splitter channels. Light storage efficiency in the beam-splitting channel can be also enhanced. Such an amplified beam splitter should have applications in optical memory, optical routers and atomic coherence control.
We theoretically investigate the properties of the eye-like ring resonator (ERR) configuration as a highly sensitive temperature sensor. We theoretically calculate the temperature sensitivity and the temperature detection precision of the configuration as a temperature sensor. The temperature sensitivity and the temperature detection precision of our configuration can achieve 837.91/ °C and 0.015°C respectively. Furthermore, we optimize the parameters of the proposed ERR configuration to enhance the temperature sensitivity and the temperature detection precision. This proposed structure enables highly sensitive, compact and stable temperature sensors.
We consider rotational Doppler effect that is related to appearing of additional optical phase using an ultra- dispersive medium. We have theoretically shown that the effect can be observed. It has been shown that the change of phase is sensitive to the rotational mechanical motion and can be used to measurement of possible rotational detection as small as 10−11 s−1/Hz1/2.
We present an entirely linear all-optical method of dispersion enhancement that relies on mode coupling between the orthogonal polarization modes of a single optical cavity, eliminating the necessity of using an atomic medium to produce the required anomalous dispersion, which decreases the dependence of the scale factor on temperature and increases signal-to-noise by reducing absorption and nonlinear effects. The use of a single cavity results in common mode rejection of the noise and drift that would be present in a system of two coupled cavities. We show that the scale-factor-to-mode-width ratio is increased above unity for this system and demonstrate tuning of the scale factor by (i) directly varying the mode coupling via rotation of an intracavity half wave plate, and (ii) coherent control of the cavity reflectance which is achieved simply by varying the incident polarization superposition. These tuning methods allow us to achieve unprecedented enhancements in the scale factor and in the scale-factor-to-mode-width ratio by closely approaching the critical anomalous dispersion condition.
Slow light in liquid crystal media o ers the way of implementing interferometric measurements in large area, easily recon gurable and highly sensitive devices. Here we present two different ways of achieving slow light in liquid crystal media, namely, photoisomerization induced transparency in dye-doped chiral liquid crystals and two-wave mixing optical resonance in pure nematics. The two mechanisms arise from absorption, respectively, refractive index gratings induced in the medium. Doppler shift measurements and adaptive holography are shown as examples of optical sensing applications.
Dynamic Brillouin gratings (DBGs), inscribed by co-modulating two writing pump waves with a bi-phase code, are analyzed theoretically, simulated numerically, demonstrated and characterized experimentally. A comparison is made between modulation by pseudo-random bit sequences (PRBS) and perfect Golomb codes. Numerical analysis shows that Golomb codes provide lower off-peak reflectivity, due to the unique properties of their cyclic auto-correlation function. Golomb coded DBGs can therefor allow for the long variable delay of one-time probe waveforms with higher signal-tonoise ratios, and without averaging. A figure of merit is proposed, in terms of the optical signal-to-noise ratio of reflected waveforms and the delay-bandwidth product of the setup. As an example, the variable delay of return-to-zero, on-off keyed data at 1 Gbit/s rate, by as much as 10 ns, is successfully demonstrated. The eye diagram of the reflected waveform remains open, whereas PRBS modulation of the pump waves results in a closed eye.
To change the group velocity of optical signals has a lot of possible applications in telecommunications, sensing, nonlinear optics and so on. Especially the exploitation of the effect of stimulated Brillouin scattering (SBS) in optical fibers is of special interest since it just requires standard telecom equipment and low to moderate optical power. However, each delay in one single, low-gain SBS based slow-light system is accompanied by pulse broadening. This is a result of the inherent Kramers-Kronig relations between the gain, the phase-change and the accompanied group velocity. For an ideal flat gain the phase-change is non-ideal, and for an ideal phase-change the gain curve leads to a broadening. Furthermore, if the gain bandwidth is broadened in order to adapt it to the signal, the delay will be reduced. Thus, for one single low-gain slow-light system the broadening can be reduced by several methods but it cannot be zero. Here we will show how a zero-broadening SBS based slow-light system can be achieved by two different methods. The basic idea is a reshaping of the original pulse by an adapted gain in a second stage. This adaptation is achieved by the superposition of two Gaussian gain profiles or by a single saturated gain. As will be shown, these systems show an almost ideal over-all gain and phase function over the bandwidth of the pulses. Thus, SBS based slow-light with a delaybandwidth product of more than 1 bit and zero distortion is possible.
The throughput of a single fiber-coupled whispering-gallery microresonator, such as a fused-silica microsphere, can exhibit induced transparency or absorption, leading to pulse delay or advancement, through the interaction of two coresonant orthogonally polarized whispering-gallery modes having very different quality factors (Q). There are two ways by which these behaviors may be realized. The first method, coupled-mode induced transparency and absorption (CMIT, CMIA), relies on intracavity cross-polarization coupling when only one mode is driven. The second method, coresonant polarization induced transparency and absorption (CPIT, CPIA), uses a simple superposition of orthogonal throughputs (in the absence of intracavity cross-polarization mode coupling) when the two modes are simultaneously driven. In both cases, the throughput behavior is observed on the same polarization component as that of the linearly polarized input. The pulse delay or advancement can be enhanced by taking advantage of the multimode capability of the tapered-fiber coupler, an advantage that is not available to free-space-beam-driven ring resonators. Some predictions of a numerical model for this enhancement, which assumes experimentally realistic conditions, are presented here.
We demonstrate the electromagnetically induced transparency like spectrum in the nested fiber ring resonator with the transfer matrix theory; the system consists of two rings and two waveguides which are connected by four couplers. The simulation results show that the tunable group delay can be realized by changing the coupling coefficients. At transmission window, the transmittance can achieve approximately 97.2% with the 0.05ns group delay. Through tuning the coupling coefficients, the group delay can vary from 0.05ns to -21.23ns and the bandwidth of the transparency window can vary from 37MHz to 15MHz.The ability for realizing such transparency resonance and for controlling the group delay or the bandwidth of such resonance is important for applications such as optical switching, as well as tunable bandwidth filter applications.
We report the experimental observation of dispersion transition from abnormal dispersion (fast light) to normal dispersion (slow light) in a side-coupled ring resonator. We reveal that the transition from fast light to slow light can occur, when the tuned loss of the resonator results in the experience from the undercoupled regime to the overcoupled regime. Also, we experimentally fabricate the fiber side-coupled ring resonator, and measure the group delay of the resonator by coupling the resonator to a fiber Mach-Zehnder interferometer (MZI). The measured experimental results demonstrate the dispersion transition, and are in good agreement with the corresponding theoretical results. The sidecoupled resonator with the tunable dispersion (group delay) can exploited for optical storage devices, slow light Fourier transform (FT) interferometric spectrometers, white light cavities (WLCs), optical switches, optical routers, and optical sensors.
We present a theoretical study of a trap-door optical buffer based on a coupled microrings add/drop filter (ADF) utilizing the white light cavity (WLC). The buffer “trap-door” can be opened and closed by tuning the resonances of the microrings comprising the ADF and trap/release optical pulses. We show that the WLC based ADF yields a maximally flat filter which exhibits superior performances in terms of bandwidth and flatness compared to previous design approaches. We also present a realistic, Silicon-over-Insulator based, design and performance analysis taking into consideration the realistic properties and limitations of the materials and the fabrication process, leading to delays exceeding 850ps for 80GHz bandwidth, and a corresponding delay-bandwidth product of approximately 70.
Proc. SPIE 8998, Progress towards atomic vapor photonic microcells: atomic polarization decoherence of Zeeman levels in rubidium
filled HC-PCF, 89981O (27 March 2014); https://doi.org/10.1117/12.2047537
We report a study on de-phasing mechanisms in Rb-filled hypocycloidal core shape Kagome hollowcore photonic crystal fibers. We experimentally measure the atomic polarization relaxation rates in Rb loaded bare silica Kagome hollow-core photonic crystal fibers at six different geometries. The measurements show a polarization relaxation time ranging from from ~ 16 μs for a 30 μm core inner-diameter HC-PCF to ~34 μs for a 96 μm core inner-diameter HC-PCF. The measured polarization lifetimes are much longer than the typical transit time for the atomic vapor at room temperature. We perform the theoretical analysis of the mechanisms of atomic de-coherence taking to account the fiber geometries and further experimental parameters. The analysis demonstrates that at given experimental conditions the main contribution to the polarization rotation signal comes from the transversally slow atoms. The effective temperature of the polarized atoms is than lower than the room temperature. We perform the Monte-Carlo simulations to calculate the atomic polarization relaxation rate in fibers with different inner core radius and negative curvature parameters. The calculated values are in a good agreement with the experimental results.
A high-storage efficiency and long-live quantum memory for photons is an essential component for the information processing in long-distance quantum communication and optical quantum computation. We demonstrated a 78% storage efficiency (SE) of coherent light pulses with a cold atomic medium based on the effect of electromagnetically induced transparency (EIT). We also obtained a large fractional delay of 74 at 50% SE, which is the best record to date. The measured fidelity of the memory is better than 90%. The results suggest the EIT light-matter interface can be readily applied to single-photon quantum states. Our work greatly advances the technology of EIT-based quantum memory for the practical quantum information applications.