Derivatization of surface-bound peptides for mass spectrometric detection via threshold single photon ionization

Chemical derivatization of peptides allows efficient F2 laser single photon ionization (SPI) of Fmoc-derivatized peptides covalently bound to surfaces. Laser desorption photoionization mass spectrometry using 337-nm pulses for desorption and 157.6-nm pulses for threshold SPI forms large ions identified as common peptide fragments bound to either Fmoc or the surface linker. Electronic structure calculations indicate the Fmoc label is behaving as an ionization tag for the entire peptide, lowering the ionization potential of the complex below the 7.87-eV photon energy. This method should allow detection of many molecular species covalently or electrostatically bound to surfaces.     

Monolithic diamond optics for single photon detection

In this work, we experimentally demonstrate a novel and simple approach that uses off-the-shelf optical elements to enhance the collection efficiency from a single emitter. The key component is a solid immersion lens made of diamond, the host material for single color centers. We improve the excitation and detection of single emitters by one order of magnitude, as predicted by theory.     

Transferring the spatial state of an entangled photon pair to a single photon by photon detection

We show theoretically that the spatial state of entangled photons generated by parametric down-conversion can be transferred to the spatial state of an idler photon by signal photon detection. This study considered the general condition with an arbitrary pump field profile and the detection of a signal photon at an arbitrary distance from a nonlinear crystal where the entangled photons are generated. Upon the detection of a signal photon, the two-photon state function of the entangled state can be transferred to a single-photon state function of the idler field due to the EPR type correlation between the signal and idler fields. The spatial state of the idler field contains more information on the original two-photon state.     

Recent progress on cooled avalanche photodiodes for single photon detection

Abstract

Recent results on the properties of cooled avalanche photodiodes for single photon detection are presented. Results from Hamamatsu silicon photodiodes, originally developed as radiation-hard photodetectors for high energy physics experiments, are extremely encouraging. Gains of approximately 10,000 can be achieved with the APD operating in proportional mode. Together with a low noise amplifier they allow photon counting with extremely high efficiency and very low noise making cold APDs almost ideal single photon detectors. Operation of APDs in Geiger mode is also reported, together with measurements of detection efficiency and noise as function of operating voltage. Prospects and hopes for future work are briefly summarized.     

High frequency optoacoustic arrays using etalon detection

Two-dimensional phased arrays for high frequency (>30 MHz) ultrasonic imaging are difficult to construct using conventional piezoelectric technology. A promising alternative involves optical detection of ultrasound, where the array element size is defined by the focal spot of a laser beam. Element size and spacing on the order of a few microns are easily achieved, suitable for imaging at frequencies exceeding 100 MHz. We have previously shown images made from a receive-only, two-dimensional optoacoustic array operating at 10 to 50 MHz. The main drawback of optical detection has been poor sensitivity when compared with piezoelectric detection. In this paper, we explore a different form of optical detection demonstrating improved sensitivity and offering a potentially simple method for constructing two-dimensional arrays. Results from a simple experiment using an etalon sensor confirm that the sensitivity of etalon detection is comparable with piezoelectric detection. This paper concludes with a proposal for a high frequency optoacoustic array system using an etalon.     

Performance of superconducting nanowire single photon detection system with different temperature variation

The performance of cryocooler-based superconducting single photon detection system suffers from the intrinsic temperature oscillation, which is typically ∼300 mK around 4.2 K originated from the periodic expansion of the cryocooler’s working fluid (He). By using a rare-earth alloy (ErNi) plate with a high heat capacity at cryogenic temperatures in between the cold head of the cryocooler and the detector block, the detector temperature variation is successfully damped to be less than 10 mK. The dark count rate is reduced and the maximum working bias current is increased. The quantum efficiency of SNSPD system is significantly improved by 40%.     

Fiber-integrated diamond-based single photon source

An alignment free, micrometer-scale single photon source consisting of a single quantum emitter on an optical fiber operating at room temperature is demonstrated. It easily integrates into fiber optic networks for quantum cryptography or quantum metrology applications.(1) Near-field coupling of a single nitrogen-vacancy center is achieved in a bottom-up approach by placing a preselected nanodiamond directly on the fiber facet. Its high photon collection efficiency is equivalent to a far-field collection via an objective with a numerical aperture of 0.82. Furthermore, simultaneous excitation and re-collection through the fiber is possible by introducing a fiber-connected single emitter sensor.     

单模太赫兹半导体激光器高精度调谐特性研究

大量物质的特征吸收谱在太赫兹范围内,因此近年来太赫兹光谱应用的发展备受关注。相比于现有的商业光谱仪,基于可调谐单模激光器的光谱测量方法具有高精度和高光谱获取速度的优势。太赫兹量子级联激光器是可调谐激光源的理想选择。在利用其实现光谱测量前,需对其调谐特性进行研究,但是现有测量方法受到精度限制。研究发现,利用太赫兹量子级联光频梳和单模激光器之间的拍频,可在微波波段得到对应的拍频信号。当调谐单模激光器时,拍频信号会发生相应的频移。因此,结合量子级联激光器的自探测,利用频谱分析仪测量拍频信号的频移情况,可以实现对单模激光器调谐的高精度测量。最终得到所测太赫兹单模激光器的调谐速率为53 MHz/K（温度调谐）和2.7 MHz/mA（电流调谐）。     

High diffraction efficiency from one- and two-dimensional Nyquist frequency binary-phase gratings

We examine the diffraction properties of one- and two-dimensional binary-phase gratings encoded onto pixelated liquid crystal displays (LCDs). We find that the first-order diffracted intensity from these binary-phase patterns can reach 100% of the zero-order intensity when the period of the grating approaches the Nyquist limit of the LCD. Experimental results show excellent agreement with theoretical predictions. This is a surprising result that has a number of implications for the encoding of diffractive optical elements.     

Pulse shapes in single photon,single particle calorimeters

Single photon or single particle calorimeters with energy resolutions of order 1 eV fwhm have recently been proposed as detectors for X-ray astronomy and many other applications. Such devices consist, essentially, of an absorber (linked to a heat bath at ∼ 0.1 K) and one or more thermistors The temperature rise induced in the former element by the absorption of a single photon or particle produces voltage waveforms at the ouput of the latter from which energy information may be abstracted. In this paper, we consider the practical limits to the energy resolution which arise from the “thermal nonuniformity” of the absorber mass. The variation in thermistor pulse shape with position of photon absorption is estimated from solutions of the heat conduction equation, for a number of linear calorimeter designs. An assessment is made of the position-sensing properties of a calorimeter with two line-end thermistors.     

Radiometric calibration of single photon detectors by a single photon source based on NV-centers in diamond

A widespread use of various relative calibration techniques is established in order to realize reliable and low uncertainty measurements of the detection efficiency, which is one key parameter characterizing single photon detectors. In the following paper we will present an approach to evaluate the relative detection efficiency of single photon avalanche photo diode (SPAD) detectors compared to a standard detector. This calibration technique is based upon the fiber-coupled relative efficiency calibration of analogue detectors, used in fiber-optic communication. For the first time, to our knowledge, an intrinsic single photon source based on the nitrogen-vacancy center in diamond was used for this purpose. Furthermore, the possible influence of different photon statistics, arising from different irradiation sources like thermal sources or lasers on the calibration results for the fiber exchange method has been theoretically studied.     

Performance analysis of different pixel-wise processing methods for depth imaging with single photon detection data

We establish a long-range single photon counting three-dimensional (3D) imaging system based on cage optical structure. Five different pixel-wise processing methods for time-of-flight (TOF) photon counting data are compared with data collected by our 3D imaging system for ranges 40–700?m and a suitable representation model for photon counting data is proposed for pixel-wise processing. Experimental results show that these methods exploit the instrumental response function (IRF), yielding a high-quality 3D image. When the signal photon counts are greater than 13 per pixel, the resulting mean absolute error (MAE) values of the IRF-based methods are better than results from the non-IRF-based methods. Regarding IRF-based methods, the union of subspace (UOS) model-based approach and cross correlation are more suitable than the Markov chain Monte Carlo (MCMC) method in the condition of a small number of return signal photons. These results offer valuable information to promote the implementation of photon counting 3D imaging in real applications.     

Reversible polarization control of single photon emission

We present reversible and a-priori control of the polarization of a photon emitted by a single molecule by introducing a nanoscale metal object in its near field. It is experimentally shown that, with the metal close to the emitter, the polarization ratio of the emission can be varied by a factor of 2. The tunability of polarization decays, when the metal is displaced by typically 30 nm. Calculations based on the multiple multipole method agree well with our experiments and predict even further enhancement with a suitable nanoantenna design.     

Understanding the up-conversion dynamics in high efficiency Yb-Tm systems for solar cells

Up-conversion emission processes have been studied in a transparent oxyfluoride nano-structured glass-ceramic co-doped with Yb³⁺ and Tm³⁺ ions. The decay and rise times, and pump power dependence of the different emission peaks have been analysed. The aim was to achieve a complete picture of the dynamics in this multiphoton excitation system. A method based on balance equations for the involved energy levels has been proposed in order to evaluate the up-conversion and decay rates from these levels. The results are analysed from the point of view of potential application to photovoltaic cells.     

Plasmonic detection of mercury via amalgam formation on surface-immobilized single Au nanorods

Abstract

Au nanorods were used as plasmonic transducers for investigation of mercury detection through a mechanism of amalgam formation at the nanorod surfaces. Marked scattering color transitions and associated blue shifts of the surface plasmon resonance peak wavelengths (λ_max) were measured in individual nanorods by darkfield microscopy upon chemical reduction of Hg(II). Such changes were related to compositional changes occurring as a result of Hg–Au amalgam formation as well as morphological changes in the nanorods’ aspect ratios. The plot of λ_max shifts vs. Hg(II) concentration showed a linear response in the 10–100 nM concentration range. The sensitivity of the system was ascribed to the narrow width of single nanorod scattering spectra, which allowed accurate determination of peak shifts. The system displayed good selectivity as the optical response obtained for mercury was one order of magnitude higher than the response obtained with competitor ions. Analysis of mercury content in river and tap water were also performed and highlighted both the potential and limitation of the developed method for real sensing applications.     

Distributed light delivery and detection via single optical fiber and tilted grating

A passive fiber-optic-based device is designed and analyzed, capable of delivering and detecting light separately or simultaneously at discrete points of interest along the optical axis of a fiber. This goal is achieved by implementation of multiple finite-length tilted gratings inside the core of a single-mode fiber. Each grating is tuned to function as a leaky electromagnetic resonator that resonates at particular wavelength and partially radiates the optical power to the medium surrounding the fiber. First, the basic element of such radiators is theoretically analyzed and a sequence of justifiable approximations are presented to measure the characteristic parameters of the system. Next, a set of equations are developed to provide a logical procedure for the design. This device has several potential applications in the field of fiber optic sensors. Few practical examples of such applications, particularly for optical stimulation of cells and fluorescence signal recording in sensitive tissues including the brain, are studied.     

Measuring the absolute photodetection efficiency using photon number correlations

We present two methods for determining the absolute detection efficiency of photon-counting detectors directly from their singles rates under illumination from a nonclassical light source. One method is based on a continuous variable analog to coincidence counting in discrete photon experiments, but it does not actually rely on high detector time resolutions. The second method is based on difference detection, which is a typical detection scheme in continuous variable quantum optics experiments. Since no coincidence detection is required with either method, they are useful for detection efficiency measurements of photodetectors with detector time resolutions far too low to resolve coincidence events.     

Multiexciton generation by a single photon in nanocrystals

We have theoretically shown that efficient generation of multi-electron-hole pairs by a single photon observed recently in semiconductor nanocrystals1-4 is caused by breaking the single electron approximation for carriers with kinetic energy above the effective energy gap. Due to strong Coulomb interaction, these states form a coherent superposition with charged excitons of the same energy. This concept allows us to define the conditions for dominant two-exciton generations by a single photon: the thermalization rate of a single exciton, initiated by light, should be lower than both the two-exciton state thermalization rate and the rate of Coulomb coupling between single and two exciton states. Possible experimental manifestations of our model are discussed.     

Thermal noise and correlations in photon detection

The standard expressions for the noise that is due to photon fluctuations in thermal background radiation typically apply only for a single detector and are often strictly valid only for single-mode illumination. I describe a technique for rigorously calculating thermal photon noise, which allows for arbitrary numbers of optical inputs and detectors, multiple-mode illumination, and both internal and external noise sources. Several simple examples are given, and a general result is obtained for multimode detectors. The formalism uses scattering matrices, noise correlation matrices, and some fundamentals of quantum optics. The covariance matrix of the photon noise at the detector outputs is calculated and includes the Hanbury Brown and Twiss photon-bunching correlations. These correlations can be of crucial importance, and they explain why instruments such as autocorrelation spectrometers and pairwise-combined interferometers are competitive (and indeed common) at radio wavelengths but have a sensitivity disadvantage at optical wavelengths. The case of autocorrelation spectrometers is studied in detail.     

Recent achievements in single photon detectors and their applications

Abstract

Solid state single photon detectors are receiving more and more attention in a number of areas of applied physics: optical sensors, communications, quantum cryptography, optical ranging and Lidar, time resolved spectroscopy, opaque media imaging and ballistic photon identification. This paper reports on results of research and development in the field of solid state single photon detectors at the Czech Technical University in Prague over the last 20 years. Avalanche photodiodes specifically designed for single photon counting devices have been developed based on various semiconductor materials: Si, Ge, GaP, GaAs and InGaAs. Electronic circuits for biasing, quenching and control of these detectors have been developed and optimized for different applications. The sensitivity of solid state photon counters spans from 0.1 nanometre X-rays up to 1800 nanometres in the near infrared region. Timing resolution of solid state photon counters as high as 50 picoseconds full width at a half maximum has been achieved when detecting single photon signals. Circuits permitting operation of solid state photon counters in both single and multiple photon signal regimes have been developed and applied. The compact and rugged design, radiation resistance, and low operating voltage are attractive features of solid state photon counters in various space projects.