We study the nonlinear optical up-conversion of doubly resonant GaP metasurfaces based on bound state in the continuum (BIC) resonances driven by leaky-waveguide modes. The fabricated metasurface is simultaneously illuminated by two excitation beams, pump and signals beams, exciting transverse-electric and -magnetic waveguide modes. The nonlinear mixing of these modes results in generation of strong sum-frequency emission in the visible spectrum. We observe a non-trivial dependence of the sum-frequency emission with the polarization of the pump beam, explained by the excitation of multipoles at the SFG wavelength. A normalized conversion efficiency of 3.5 × 10-5 [W-1] is measured in the forward direction.
KEYWORDS: Avalanche photodetectors, Field programmable gate arrays, System on a chip, Quenching (fluorescence), Sensors, Custom fabrication, Single photon, Microcontrollers, Single photon detectors, Reconfigurable computing
Most active quench circuits used for single-photon avalanche detectors are designed either with discrete components which lack the flexibility of dynamically changing the control parameters, or with custom ASICs which require a long development time and high cost. As an alternative, we present a reconfigurable and robust hybrid design implemented using a System-on-Chip (SoC), which integrates both an FPGA and a microcontroller. We take advantage of the FPGA’s speed and configuration capabilities to vary the quench and reset parameters dynamically over a large range, thus allowing our circuit to operate with a wide variety of APDs without having to re-design the system. The microcontroller enables the remote adjustment of control parameters and re-calibration of APDs in the field. The ruggedized design uses components with space heritage, thus making it suitable for space-based applications in the fields of telecommunications and quantum key distribution (QKD). We characterize our circuit with a commercial APD cooled to -20°C, and obtain a deadtime of 35ns while maintaining the after-pulsing probability at close to 3%. We also demonstrate versatility of the circuit by directly testing custom fabricated chip-scale APDs, which paves the way for automated wafer-scale testing and characterization.
We describe a proof-of-concept of a method for measurement of both real (refraction) and imaginary (absorption) part of
the refractive index in the infrared (IR) range by measuring an interference pattern in the visible range without the need
for any spectral and spatial selection. The concept is based on nonlinear interference of entangled photons, generated via
Spontaneous Parametric Down Conversion (SPDC). In our interferometer, the phase of the signal photon in the visible
range depends on the phase of an entangled IR photon. When the IR photon is traveling through the media of interest, its
properties can be found from the observations of the visible photon.
Harnessing entanglement as a resource is the main workhorse of many quantum protocols, and establishing the degree of quantum correlations of quantum states is an important certification process that has to take place prior to any implementations of these quantum protocols. The emergence of photodetectors known as photon-number-resolving detectors (PNRDs) that allow for accounting of photon numbers simultaneously arriving at the detectors has led to the need for modeling accurately and applying them for use in the certification process. Here we study the variance of difference of photocounts (VDP) of two PNRDs, which is one measure of quantum correlations, under the effects of loss and saturation. We found that it would be possible to distinguish between the classical correlation of a two-mode coherent state and the quantum correlation of a twin-beam state within some photo count regime of the detector. We compare the behavior of two such PNRDs. The first for which the photocount statistics follow a binomial distribution accounting for losses, and the second is that of Agarwal, Vogel, and Sperling for which the incident beam is first split and then separately measured by ON/OFF detectors. In our calculations, analytical expressions are derived for the variance of difference where possible. In these cases, Gauss' hypergeometric function appears regularly, giving an insight to the type of quantum statistics the photon counting gives in these PNRDs. The different mechanisms of the two types of PNRDs leads to quantitative differences in their VDP.
In this paper we review our recent works on the generation of different Bell states within the lineshape of
parametric down-conversion (SPDC) and their possible applications. Indeed, for polarization-entangled two-photon
states produced via SPDC, the frequency-angular lineshape allowed by phase matching is considered. It
is shown that there are always different Bell states generated for different mismatch values within the natural
bandwidth. Consideration is made for two different methods of polarization entanglement preparation, based on
type-II SPDC and on SPDC in two type-I crystals producing orthogonally polarized photon pairs. Different Bell
states can be filtered out by either frequency selection or angular selection, or both. Our theoretical calculations
are confirmed by a series of experiments, performed for the two above-mentioned ways of producing polarization-entangled
photon pairs and with two kinds of measurements: frequency-selective and angular-selective. Finally, we mention possible application to quantum communication with fibers.
In this paper we will present some experimental researches about Quantum Communication performed in "Carlo Novero" Quantum Optics laboratory at INRiM (former IEN). After a general review of our studies, we will describe our recent researches on propagation of polarization entangled photons in optical fibres focused on the investigation of the effect of two-photon interference in the second-order Glauber's correlation function and on the characterization of this quantum channel as a Complete Positive (CP) map. We will then describe an innovative method, based on detectors operating in Geiger mode (on/off), for reconstructing the photon statistics of quantum optical states, presenting experimental data collected to test the extension of this method to multi-partite states.
Our last experimental results on the realization of a measurement-conditional unitary operation at single photon level are presented. This gate operates by rotating by 90° the polarization of a photon produced by means of Type-II Parametric Down Conversion conditional to a polarization measurement on the correlated photon. We then propose a new scheme for measuring the quantum efficiency of a single photon detection apparatus by using this set-up. We present experimental results obtained with this scheme compared with traditional biphoton calibration. Our results show the interesting potentiality of the suggested scheme.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.