Event-Locked Time-Resolved Fourier Spectroscopy

A low-cost method of adding time-resolving capability to commercial Fourier transform spectrometers with a continuously scanning Michelson interferometer has been developed. This method is specifically designed to eliminate noise and artifacts caused by mirror-speed variations in the interferometer. The method exists of two parts: (1) a novel timing scheme for synchronizing the transient events under study and the digitizing of the interferogram and (2) a mathematical algorithm for extracting the spectral information from the recorded data. The novel timing scheme is a modification of the well-known interleaved, or stroboscopic, method. It achieves the same timing accuracy, signal-to-noise ratio, and freedom from artifacts as step-scan time-resolving Fourier spectrometers by locking the sampling of the interferogram to a stable time base rather than to the occurrences of the HeNe fringes. The necessary pathlength-difference information at which samples are taken is obtained from a record of the mirror speed. The resulting interferograms with uneven pathlength-difference spacings are transformed into wavenumber space by least-squares fits of periodic functions. Spectra from the far-infrared to the upper visible at resolutions up to 0.2 cm−1 are used to demonstrate the utility of this method.

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Megahertz scan rates enabled by optical sampling by repetition-rate tuning

Scientific Reports ◽

10.1038/s41598-021-02502-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

D. Bajek ◽

M. A. Cataluna

Keyword(s):

Real Time ◽

Repetition Rate ◽

Low Cost ◽

Impedance Matching ◽

Michelson Interferometer ◽

Laser Source ◽

Time Resolved ◽

Time Resolved Spectroscopy ◽

Optical Sampling ◽

Probe Spectroscopy

AbstractWe demonstrate, for the first time, optical sampling by repetition-rate tuning (OSBERT) at record megahertz scan rates. A low-cost, tunable and extremely compact 2-section passively mode-locked laser diode (MLLD) is used as the pulsed laser source, whose repetition rate can be modulated electronically through biasing of the saturable absorber section. The pulsed output is split into two arms comparable to an imbalanced Michelson interferometer, where one arm is significantly longer than the other (a passive delay line, or PDL). The resulting electronic detuning of the repetition rate gives rise to a temporal delay between pulse pairs at a detector; the basis for time-resolved spectroscopy. Through impedance-matching, we developed a new system whereby a sinusoidal electrical bias could be applied to the absorber section of the MLLD via a signal generator, whose frequency could be instantly increased from sub-hertz through to megahertz modulation frequencies, corresponding to a ground-breaking megahertz optical sampling scan rate, which was experimentally demonstrated by the real-time acquisition of a cross-correlation trace of two ultrashort optical pulses within just 1 microsecond of real time. This represents scan rates which are three orders of magnitude greater than the recorded demonstrations of OSBERT to date, and paves the way for highly competitive scan rates across the field of time-resolved spectroscopy and applications therein which range from pump probe spectroscopy to metrology.

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Far infrared absorption and rotational vibrations of the guest molecules in structure I clathrate hydrates between 4.3 and 100 K

Canadian Journal of Chemistry ◽

10.1139/v77-249 ◽

1977 ◽

Vol 55 (10) ◽

pp. 1777-1785 ◽

Cited By ~ 25

Author(s):

John E. Bertie ◽

Stephen M. Jacobs

Keyword(s):

Ethylene Oxide ◽

Guest Molecule ◽

Signal To Noise Ratio ◽

Michelson Interferometer ◽

Far Infrared ◽

Force Constants ◽

Clathrate Hydrates ◽

High Signal ◽

Guest Molecules ◽

Trimethylene Oxide

The infrared spectra between 330 and 15 cm−1 of the structure I clathrate hydrates of ethylene oxide, cyclopropane, and trimethylene oxide, at 4.3 K are presented. The spectra have an unusually high signal-to-noise ratio made possible by a Michelson interferometer and a silicon bolometer detector which operates at 1.2 K. Rotational vibrations of the guest molecules were observed at 65.0 and 35.6 cm−1 for ethylene oxide and at 69 and 50 cm−1 for trimethylene oxide. Inter-guest coupling of rotational vibrations is small and the two frequencies are assigned to vibrations about different inertial axes. The resulting force constants are 487 and 264 ferg rad−2 for ethylene oxide and 1190 and 1130 ferg rad−2 for trimethylene oxide and are discussed in relation to the barriers to reorientation of the guest molecule. The bands due to these vibrations are fairly sharp at 4.3 K, but are broad and poorly defined at 100 K. The guest and water vibrations interact predominantly through their transition dipoles, although the main contribution to the force constants of the rotational vibrations is from steric forces. The absorption by the water vibrations above 100 cm−1 is very similar for ethylene oxide and cyclopropane hydrates but significantly different for trimethylene oxide hydrate. Strong objections exist to the obvious interpretations of this difference which remains unexplained.

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Development and Evaluation of a Polarization-Division Interferometer with Cube Corner Mirrors

Applied Spectroscopy ◽

10.1366/000370202321116129 ◽

2002 ◽

Vol 56 (12) ◽

pp. 1626-1632

Author(s):

Prasad L. Polavarapu ◽

Pranati K. Bose ◽

Allan J. Rilling ◽

Henry Buijs ◽

Jean Rene Roy

Keyword(s):

Signal To Noise Ratio ◽

Michelson Interferometer ◽

Polarized Light ◽

Far Infrared ◽

Linear Dichroism ◽

Signal To Noise ◽

Cube Corner ◽

New Instrument ◽

Oriented Films ◽

Ft Ir

The use of cube corner mirrors in conventional Fourier transform infrared (FT-IR) spectrometers has led to increased stability and enhanced signal-to-noise ratio. Polarization-division interferometers for the mid- and far-infrared regions, however, were based on either the Martin–Puplett design, which utilizes roof-top mirrors, or the Michelson interferometer design, which utilizes the plane mirrors. In this paper, we report the development of a polarization-division interferometer with cube corner mirrors. In this design, two different wire-grid beamsplitters are used for the division and recombination of polarized light. The performance of this new instrument has been evaluated by measuring the linear dichroism of oriented films and the circular dichroism of isotropic samples. This development facilitates the adaptation of commonly used FT-IR spectrometers with cube corner mirrors for polarization-division configuration.

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Application of Novel Low Current OBIRCH Amplifier and Nanoprobing to Identify Subtle Leakages in Advanced Node Technologies

10.31399/asm.cp.istfa2018p0303 ◽

2018 ◽

Author(s):

Satish Kodali ◽

Liangshan Chen ◽

Yuting Wei ◽

Tanya Schaeffer ◽

Chong Khiam Oh

Keyword(s):

Signal To Noise Ratio ◽

Semiconductor Industry ◽

Fault Isolation ◽

Ring Oscillator ◽

High Signal ◽

The Novel ◽

Resistance Change ◽

Three Samples ◽

Relative Threshold ◽

First Time

Abstract Optical beam induced resistance change (OBIRCH) is a very well-adapted technique for static fault isolation in the semiconductor industry. Novel low current OBIRCH amplifier is used to facilitate safe test condition requirements for advanced nodes. This paper shows the differences between the earlier and novel generation OBIRCH amplifiers. Ring oscillator high standby leakage samples are analyzed using the novel generation amplifier. High signal to noise ratio at applied low bias and current levels on device under test are shown on various samples. Further, a metric to demonstrate the SNR to device performance is also discussed. OBIRCH analysis is performed on all the three samples for nanoprobing of, and physical characterization on, the leakage. The resulting spots were calibrated and classified. It is noted that the calibration metric can be successfully used for the first time to estimate the relative threshold voltage of individual transistors in advanced process nodes.

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A Time-Resolved Low-Angle Light Scattering Apparatus. Application to Phase Separation Problems in Polymer Systems

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20010973 ◽

2001 ◽

Vol 66 (6) ◽

pp. 973-982 ◽

Cited By ~ 5

Author(s):

Čestmír Koňák ◽

Jaroslav Holoubek ◽

Petr Štěpánek

Keyword(s):

Phase Separation ◽

Light Scattering ◽

Signal To Noise Ratio ◽

Scattered Light ◽

Ccd Camera ◽

Time Resolved ◽

Polymer Systems ◽

Software Analysis ◽

Phase Separation Kinetics ◽

Small Angle Light Scattering

A time-resolved small-angle light scattering apparatus equipped with azimuthal integration by means of a conical lens or software analysis of scattering patterns detected with a CCD camera was developed. Averaging allows a significant reduction of the signal-to-noise ratio of scattered light and makes this technique suitable for investigation of phase separation kinetics. Examples of applications to time evolution of phase separation in concentrated statistical copolymer solutions and dissolution of phase-separated domains in polymer blends are given.

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Efficient Estimation of CFO-Affected OFDM BER Floor in Small Cells with Resource-Limited IoT End-Points

Sensors ◽

10.3390/s20133747 ◽

2020 ◽

Vol 20 (13) ◽

pp. 3747

Author(s):

Adriana Lipovac ◽

Vlatko Lipovac ◽

Borivoj Modlic

Keyword(s):

Orthogonal Frequency Division Multiplexing ◽

Carrier Frequency Offset ◽

Signal To Noise Ratio ◽

Low Cost ◽

Error Recovery ◽

Efficient Estimation ◽

Analytical Models ◽

Small Cells ◽

End Points ◽

Power Delay Profile

Contemporary wireless networks dramatically enhance data rates and latency to become a key enabler of massive communication among various low-cost devices of limited computational power, standardized by the Long-Term Evolution (LTE) downscaled derivations LTE-M or narrowband Internet of Things (NB IoT), in particular. Specifically, assessment of the physical-layer transmission performance is important for higher-layer protocols determining the extent of the potential error recovery escalation upwards the protocol stack. Thereby, it is needed that the end-points of low processing capacity most efficiently estimate the residual bit error rate (BER) solely determined by the main orthogonal frequency-division multiplexing (OFDM) impairment–carrier frequency offset (CFO), specifically in small cells, where the signal-to-noise ratio is large enough, as well as the OFDM symbol cyclic prefix, preventing inter-symbol interference. However, in contrast to earlier analytical models with computationally demanding estimation of BER from the phase deviation caused by CFO, in this paper, after identifying the optimal sample instant in a power delay profile, we abstract the CFO by equivalent time dispersion (i.e., by additional spreading of the power delay profile that would produce the same BER degradation as the CFO). The proposed BER estimation is verified by means of the industry-standard LTE software simulator.

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Experimental demonstration of spectral domain computational ghost imaging

Scientific Reports ◽

10.1038/s41598-021-87355-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Piotr Ryczkowski ◽

Caroline G. Amiot ◽

John M. Dudley ◽

Goëry Genty

Keyword(s):

Signal To Noise Ratio ◽

Michelson Interferometer ◽

Spectral Domain ◽

Proof Of Concept ◽

Ghost Imaging ◽

Spectral Measurements ◽

Spectral Filter ◽

Wavelength Division ◽

Spectral Encoding ◽

Light Effects

AbstractWe demonstrate computational spectral-domain ghost imaging by encoding complementary Fourier patterns directly onto the spectrum of a superluminescent laser diode using a programmable spectral filter. Spectral encoding before the object enables uniform spectral illumination across the beam profile, removing the need for light collection optics and yielding increased signal-to-noise ratio. In addition, the use of complementary Fourier patterns allows reduction of deleterious of parasitic light effects. As a proof-of-concept, we measure the wavelength-dependent transmission of a Michelson interferometer and a wavelength-division multiplexer. Our results open new perspectives for remote broadband spectral measurements.

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Pocket MUSE: an affordable, versatile and high-performance fluorescence microscope using a smartphone

Communications Biology ◽

10.1038/s42003-021-01860-5 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Yehe Liu ◽

Andrew M. Rollins ◽

Richard M. Levenson ◽

Farzad Fereidouni ◽

Michael W. Jenkins

Keyword(s):

High Performance ◽

Point Of Care ◽

Low Cost ◽

Consumer Electronics ◽

Practical Implementation ◽

The Novel ◽

Point Of Care Diagnostics ◽

Optical Module ◽

Optical Configuration ◽

User Friendly

AbstractSmartphone microscopes can be useful tools for a broad range of imaging applications. This manuscript demonstrates the first practical implementation of Microscopy with Ultraviolet Surface Excitation (MUSE) in a compact smartphone microscope called Pocket MUSE, resulting in a remarkably effective design. Fabricated with parts from consumer electronics that are readily available at low cost, the small optical module attaches directly over the rear lens in a smartphone. It enables high-quality multichannel fluorescence microscopy with submicron resolution over a 10× equivalent field of view. In addition to the novel optical configuration, Pocket MUSE is compatible with a series of simple, portable, and user-friendly sample preparation strategies that can be directly implemented for various microscopy applications for point-of-care diagnostics, at-home health monitoring, plant biology, STEM education, environmental studies, etc.

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All-Optical Non-Inverted Parity Generator and Checker Based on Semiconductor Optical Amplifiers

Applied Sciences ◽

10.3390/app11041499 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1499

Author(s):

Bingchen Han ◽

Junyu Xu ◽

Pengfei Chen ◽

Rongrong Guo ◽

Yuanqi Gu ◽

...

Keyword(s):

Optical Amplifiers ◽

Signal To Noise Ratio ◽

Low Cost ◽

Extinction Ratio ◽

Semiconductor Optical Amplifiers ◽

Optical Signal ◽

Probe Light ◽

All Optical ◽

Negative Effect ◽

Parity Generator

An all-optical non-inverted parity generator and checker based on semiconductor optical amplifiers (SOAs) are proposed with four-wave mixing (FWM) and cross-gain modulation (XGM) non-linear effects. A 2-bit parity generator and checker using by exclusive NOR (XNOR) and exclusive OR (XOR) gates are implemented by first SOA and second SOA with 10 Gb/s return-to-zero (RZ) code, respectively. The parity and check bits are provided by adjusting the center wavelength of the tunable optical bandpass filter (TOBPF). A saturable absorber (SA) is used to reduce the negative effect of small signal clock (Clk) probe light to improve extinction ratio (ER) and optical signal-to-noise ratio (OSNR). For Pe and Ce (even parity bit and even check bit) without Clk probe light, ER and OSNR still maintain good performance because of the amplified effect of SOA. For Po (odd parity bit), ER and OSNR are improved to 1 dB difference for the original value. For Co (odd check bit), ER is deteriorated by 4 dB without SA, while OSNR is deteriorated by 12 dB. ER and OSNR are improved by about 2 dB for the original value with the SA. This design has the advantages of simple structure and great integration capability and low cost.

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Core–Shell Chain-Like Cu@Ni Composite with Dual Absorption Peaks to Improve Microwave Absorption Properties

NANO ◽

10.1142/s1793292018500522 ◽

2018 ◽

Vol 13 (05) ◽

pp. 1850052

Author(s):

Yuanyuan Zhou ◽

Jianying Deng ◽

Shimei Li ◽

Zefeng Li

Keyword(s):

Hydrothermal Reaction ◽

Low Cost ◽

Electromagnetic Properties ◽

Formation Mechanisms ◽

Core Shell ◽

The Novel ◽

Redox Potentials ◽

X Ray Diffraction ◽

Ni Alloy ◽

Absorbing Material

Core–shell Cu@Ni chains were successfully synthesized through a mild hydrothermal reaction. The morphology, structure and microwave electromagnetic properties of the composite were then characterized by X-ray diffraction, energy-dispersive spectroscopy, scanning electron microscopy and vector network analysis. The formation mechanisms of the core–shell structure and one-dimensional chains were ascribed to the varying redox potentials of Cu and Ni ions and the magnetic dipole–dipole attraction. Furthermore, a minimal reflection loss (RL) of [Formula: see text]20.7[Formula: see text]dB was observed at 9.6[Formula: see text]GHz with a thickness of 2.0[Formula: see text]mm and the effective absorption ([Formula: see text]10[Formula: see text]dB, 90% microwave attenuation) bandwidth can be adjusted between 5.2[Formula: see text]GHz and 16.6[Formula: see text]GHz for the thin absorber thickness of 2.0–4.0[Formula: see text]mm. The novel core–shell chain-like Cu@Ni alloy can be used as a promising absorbing material because it shows numerous features such as thin thickness, strong absorption, low cost and lightweight.

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