Ilkka Nissinen

Bio: Ilkka Nissinen is an academic researcher from University of Oulu. The author has contributed to research in topics: Raman spectroscopy & Single-photon avalanche diode. The author has an hindex of 14, co-authored 39 publications receiving 678 citations.

Fluorescence suppression in Raman spectroscopy using a time-gated CMOS SPAD

Abstract: A Raman spectrometer technique is described that aims at suppressing the fluorescence background typical of Raman spectra. The sample is excited with a high power (65W), short (300ps) laser pulse and the time position of each of the Raman scattered photons with respect to the excitation is measured with a CMOS SPAD detector and an accurate time-to-digital converter at each spectral point. It is shown by means of measurements performed on an olive oil sample that the fluorescence background can be greatly suppressed if the sample response is recorded only for photons coinciding with the laser pulse. A further correction in the residual fluorescence baseline can be achieved using the measured fluorescence tails at each of the spectral points.

Integrated Receiver Including Both Receiver Channel and TDC for a Pulsed Time-of-Flight Laser Rangefinder With cm-Level Accuracy

Abstract: An integrated receiver that includes both the time-to-digital converter (TDC) and the receiver channel and is intended for a pulsed time-of-flight laser rangefinder with a measurement range of approximately 10 m has been designed and fabricated in a standard 0.13 mum CMOS process. The receiver operates by detecting the current pulse of an optical detector and producing a stop timing mark for the TDC by means of a leading edge timing discriminator. The TDC is used to measure the actual time interval between the start and stop pulses and the slew-rate of the stop pulse, to compensate for a walk error produced in the discriminator. The single-shot precision of the whole receiver is 250 ps for a minimum detectable signal, and its accuracy and power consumption are plusmn 37 ps with compensation within a dynamic range of at least 1:10,000 and less than 45 mW, respectively. The size of the die is 1300 mum times1300 mum including pads.

A CMOS time-to-digital converter based on a ring oscillator for a laser radar

Abstract: An integrated ring oscillator based time-to-digital converter (TDC) for a pulsed time-of-flight laser rangefinder has been designed and tested. The time-to-digital conversion is based on counting the pulses of this eight-stage differential ring oscillator and additionally registering the state of its 16 phases at the arrival moment of the timing signals. The single-shot precision and the non-linearity of the TDC are better than 78.5ps and /spl plusmn/37ps, respectively and the current consumption of the time-to-digital converter was fabricated on the same chip with a receiver channel in a 0.35 /spl mu/m CMOS process.

A sub-ns time-gated CMOS single photon avalanche diode detector for Raman spectroscopy

Abstract: A time-gated single photon avalanche diode (SPAD) has been designed and fabricated in a standard high voltage 0.35 μm CMOS technology for Raman spectroscopy. The sub-ns time gating window is used to suppress the fluorescence background typical of Raman studies, and also to minimize the dark count rate in order to maximize the signal-to-noise ratio of the Raman signal. The proposed time-gating technique is applied for measuring the Raman spectra of olive oil with a gate window of 300 ps, and shows significant fluorescence suppression.

On Laser Ranging Based on High-Speed/Energy Laser Diode Pulses and Single-Photon Detection Techniques

Abstract: This paper discusses the construction principles and performance of a pulsed time-of-flight (TOF) laser radar based on high-speed (FWHM $\sim$ 100 ps) and high-energy ( $\sim$ 1 nJ) optical transmitter pulses produced with a specific laser diode working in an “enhanced gain-switching” regime and based on single-photon detection in the receiver. It is shown by analysis and experiments that single-shot precision at the level of 2…3 cm is achievable. The effective measurement rate can exceed 10 kHz to a noncooperative target (20% reflectivity) at a distance of $>\ 50\ \hbox{m}$ , with an effective receiver aperture size of $2.5\ \hbox{cm}^{2} $ . The effect of background illumination is analyzed. It is shown that the gating of the SPAD detector is an effective means to avoid the blocking of the receiver in a high-level background illumination case. A brief comparison with pulsed TOF laser radars employing linear detection techniques is also made.

A Multi-Path Gated Ring Oscillator TDC With First-Order Noise Shaping

Abstract: An 11-bit, 50-MS/s time-to-digital converter (TDC) using a multipath gated ring oscillator with 6 ps of effective delay per stage demonstrates 1st-order noise shaping. At frequencies below 1 MHz, the TDC error integrates to 80 fs (rms) for a dynamic range of 95 dB with no calibration required. The 157 times 258 mum TDC is realized in 0.13 mum CMOS and, depending on the time difference between input edges, consumes 2.2 to 21 mA from a 1.5 V supply.

EXPRESS: Portable Spectroscopy:

Abstract: Until very recently, handheld spectrometers were the domain of major analytical and security instrument companies, with turnkey analyzers using spectroscopic techniques from X-ray fluorescence (XRF) for elemental analysis (metals), to Raman, mid-infrared, and near-infrared (NIR) for molecular analysis (mostly organics). However, the past few years have seen rapid changes in this landscape with the introduction of handheld laser-induced breakdown spectroscopy (LIBS), smartphone spectroscopy focusing on medical diagnostics for low-resource areas, commercial engines that a variety of companies can build up into products, hyphenated or dual technology instruments, low-cost visible-shortwave NIR instruments selling directly to the public, and, most recently, portable hyperspectral imaging instruments. Successful handheld instruments are designed to give answers to non-scientist operators; therefore, their developers have put extensive resources into reliable identification algorithms, spectroscopic libraries or databases, and qualitative and quantitative calibrations. As spectroscopic instruments become smaller and lower cost, “engines” have emerged, leading to the possibility of being incorporated in consumer devices and smart appliances, part of the Internet of Things (IOT). This review outlines the technologies used in portable spectroscopy, discusses their applications, both qualitative and quantitative, and how instrument developers and vendors have approached giving actionable answers to non-scientists. It outlines concerns on crowdsourced data, especially for heterogeneous samples, and finally looks towards the future in areas like IOT, emerging technologies for instruments, and portable hyphenated and hyperspectral instruments.

Single-photon avalanche diode imagers in biophotonics: review and outlook

Abstract: Single-photon avalanche diode (SPAD) arrays are solid-state detectors that offer imaging capabilities at the level of individual photons, with unparalleled photon counting and time-resolved performance. This fascinating technology has progressed at a very fast pace in the past 15 years, since its inception in standard CMOS technology in 2003. A host of architectures have been investigated, ranging from simpler implementations, based solely on off-chip data processing, to progressively "smarter" sensors including on-chip, or even pixel level, time-stamping and processing capabilities. As the technology has matured, a range of biophotonics applications have been explored, including (endoscopic) FLIM, (multibeam multiphoton) FLIM-FRET, SPIM-FCS, super-resolution microscopy, time-resolved Raman spectroscopy, NIROT and PET. We will review some representative sensors and their corresponding applications, including the most relevant challenges faced by chip designers and end-users. Finally, we will provide an outlook on the future of this fascinating technology.

Review of Fluorescence Suppression Techniques in Raman Spectroscopy

Abstract: Raman spectroscopy is an important and powerful technique for analyzing the chemical composition of biological or nonbiological samples in many fields. A serious challenge frequently encountered in Raman measurements arises from the existence of the concurrent fluorescence background. The fluorescence intensity is normally several orders of magnitude larger than the Raman scattering signal, especially in biological samples. Such fluorescence background must be suppressed in order to obtain accurate Raman spectra. Several different techniques have been explored for this purpose. These techniques could be generally grouped into time-domain, frequency-domain, wavelength-domain, and computational methods in addition to various Raman enhancement techniques and other unconventional methods. This review briefly describes the fundamental principles of each group of methods, reports the most recent advances, and makes comparison across those major categories of techniques in terms of cost and performance i...