Flexible digital signal processing architecture for narrowband and spread-spectrum lock-in detection in multiphoton microscopy and time-resolved spectroscopy

Wilson, Jesse W.; Park, Jong Kang; Warren, Warren S.; Fischer, Martin C.

doi:10.1063/1.4916261

Cited by 13 publications

(11 citation statements)

References 30 publications

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“…94 If only slow dynamics need to be resolved, pulse synchronization requirements are greatly relaxed or can in certain cases be eliminated entirely by using a continuous-wave probe. 95 Slow dynamics can then still be recovered through the phase angle output of the lock-in or by spread-spectrum modulation, 96 but information on fast dynamics cannot be retrieved.…”

Section: Pulse Source and Synchronizationmentioning

confidence: 99%

Invited Review Article: Pump-probe microscopy

Fischer

Wilson

Robles

et al. 2016

Review of Scientific Instruments

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205

143

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Multiphoton microscopy has rapidly gained popularity in biomedical imaging and materials science because of its ability to provide three-dimensional images at high spatial and temporal resolution even in optically scattering environments. Currently the majority of commercial and home-built devices are based on two-photon fluorescence and harmonic generation contrast. These two contrast mechanisms are relatively easy to measure but can access only a limited range of endogenous targets. Recent developments in fast laser pulse generation, pulse shaping, and detection technology have made accessible a wide range of optical contrasts that utilize multiple pulses of different colors. Molecular excitation with multiple pulses offers a large number of adjustable parameters. For example, in two-pulse pump-probe microscopy, one can vary the wavelength of each excitation pulse, the detection wavelength, the timing between the excitation pulses, and the detection gating window after excitation. Such a large parameter space can provide much greater molecular specificity than existing single-color techniques and allow for structural and functional imaging without the need for exogenous dyes and labels, which might interfere with the system under study. In this review, we provide a tutorial overview, covering principles of pump-probe microscopy and experimental setup, challenges associated with signal detection and data processing, and an overview of applications.

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Section: Pulse Source and Synchronizationmentioning

confidence: 99%

Invited Review Article: Pump-probe microscopy

Fischer

Wilson

Robles

et al. 2016

Review of Scientific Instruments

Self Cite

205

143

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show abstract

“…An important consideration is whether the ADC provides enough quantization steps to resolve weak pump-probe signals. 12 We use a 14-bit ADC, operating in a

range, resulting in a quantization step of

. A CIC filter with

is used for decimation.…”

Section: Theory and Backgroundmentioning

confidence: 99%

“…Our approach builds on previous works that demonstrated the ability to extract weak pump-probe signals from digital signals acquired by an analog-to-digital converter. 11,12 The novelty here is in adding a digital adaptive filter before the lock-in.…”

Section: Introductionmentioning

confidence: 99%

Adaptive noise canceling for transient absorption microscopy

2020

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Significance: Ultrafast fiber lasers are an attractive alternative to bulk lasers for nonlinear optical microscopy for their compactness and low cost. The high relative intensity noise (RIN) of these lasers poses a challenge for pump-probe measurements such as transient absorption and stimulated Raman scattering, along with modalities that provide label-free contrast from the vibrational and electronic structure of molecules. Aim: Digital adaptive filtering was applied to determine the applicability for canceling laser RIN in a transient absorption microscope with an ultrafast fiber laser source. Approach: Digitized signals from the transmitted probe and reference photodetectors were fed to an adaptive filter in MATLAB, running in a noise canceling configuration. This result was then fed to a software lock-in algorithm to demodulate the pump-probe signal. Images were built up one line scan at a time with a 3.5-kHz resonant scanner, with 100× averaging. The imaging target was Bi 4 Ge 3 O 12 , which exhibits nondegenerate two-photon absorption at the pump/probe wavelengths used (530-nm pump and 490-nm probe). Results: Without adaptive noise cancellation, the lock-in output primarily passes the laser RIN within its detection bandwidth, resulting in images that closely follow the linear transmissivity and lack sensitivity to pump-probe time delay. With adaptive noise cancellation in front of the lock-in, the RIN rejection is enough to restore the z-sectioning and sensitivity to pump-probe delay, as expected for transient absorption. Results were limited primarily by noise from the photodetector and analog-to-digital converter. Conclusions: Digital adaptive noise cancellation, even when limited by electronics noise, can recover pump-probe signals by removal of laser RIN, under conditions where averaging alone fails.

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“…In the beginning only analogue lock-in amplifiers were implemented with tubes (Baker, 1954, Dereppe, 1961, operational amplifiers (De Marcellis et al, 2012) and applicationspecific integrated circuits (ASIC) (Ferri et al, 2001). Nowadays digital lock-in detectors implemented by discrete circuits (Saam and Conradi, 1998), digital signal processors (DSP) (Sonnaillon and Bonetto, 2005;Proksch, 2006), field programmable gate arrays (FPGA) (Wilson et al, 2015), microcontrollers (Bengtsson, 2012) or software (Andersson et al, 2007) are more common. Digital lock-in detection is more robust compared to analogue solutions.…”

Section: Introductionmentioning

confidence: 99%

A remote-control datalogger for large-scale resistivity surveys and robust processing of its signals using a software lock-in approach

Oppermann¹,

Günther²

2018

Geosci. Instrum. Method. Data Syst.

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Abstract. We present a new versatile datalogger that can be used for a wide range of possible applications in geosciences. It is adjustable in signal strength and sampling frequency, battery saving and can remotely be controlled over a Global System for Mobile Communication (GSM) connection so that it saves running costs, particularly in monitoring experiments. The internet connection allows for checking functionality, controlling schedules and optimizing pre-amplification. We mainly use it for large-scale electrical resistivity tomography (ERT), where it independently registers voltage time series on three channels, while a square-wave current is injected. For the analysis of this time series we present a new approach that is based on the lock-in (LI) method, mainly known from electronic circuits. The method searches the working point (phase) using three different functions based on a mask signal, and determines the amplitude using a direct current (DC) correlation function. We use synthetic data with different types of noise to compare the new method with existing approaches, i.e. selective stacking and a modified fast Fourier transformation (FFT)-based approach that assumes a 1/f noise characteristics. All methods give comparable results, but the LI is better than the well-established stacking method. The FFT approach can be even better but only if the noise strictly follows the assumed characteristics. If overshoots are present in the data, which is typical in the field, FFT performs worse even with good data, which is why we conclude that the new LI approach is the most robust solution. This is also proved by a field data set from a long 2-D ERT profile.

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Flexible digital signal processing architecture for narrowband and spread-spectrum lock-in detection in multiphoton microscopy and time-resolved spectroscopy

Cited by 13 publications

References 30 publications

Invited Review Article: Pump-probe microscopy

Invited Review Article: Pump-probe microscopy

Adaptive noise canceling for transient absorption microscopy

A remote-control datalogger for large-scale resistivity surveys and robust processing of its signals using a software lock-in approach

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