FLIM specifications_10052020.docx

FLIM specifications draft

The Naval Research Laboratory has a requirement for a Fluorescence Lifetime Imaging Confocal Microscope to enable time-resolved measurements of luminescent emission spectra upon photoexcitation to determine the lifetime of emitting states with single photon sensitivity and < 50 ps temporal resolution. The system shall be capable of performing lifetime measurements / lifetime mapping of wavelength resolved luminescent emission features from monolayer transition metal dichalcogenides such as MoS2, and performing antibunching measurements on single photon emitters in monolayer WSe2 with diffraction limited spatial resolution. The system shall include capabilities for wavelength analysis by both tunable bandpass filters at selected wavelengths, and gratings over a continuous range, at the choice of the user, over a range of 500-950 nm, and include three pulsed laser excitation sources.

The system must further meet the following requirements for future expansion:

a) be compatible with at least one commercially available atomic force microscope to offer tip-enhanced luminescence,

b) be compatible with at least one commercially available optical cryostat to provide controlled sample temperature over the range of 10-300 K with a working distance of 3 mm or less.

The system shall provide the following capabilities / components:

1) a confocal optical microscope column to provide diffraction limited spatial resolution;

2) a set of pulsed laser diodes with discrete wavelengths for sample excitation;

3) time resolved photoluminescence (TRPL) measurement using a wavelength tunable narrow bandpass filter with < 100ps time resolution after correction for the instrument response function;

4) single photon antibunching measurement using a wavelength tunable narrow bandpass filter and the Hanbury-Brown-Twiss (HBT) geometry with < 100ps time resolution after correction for the instrument response function;

5) a grating spectrometer for high resolution PL survey scans and time-resolved PL with 1nm spectral resolution and < 50ps time resolution after correction for the instrument response function;

6) time-correlated single photon counting electronics, all electronics and power supplies, and control and analysis software necessary to operate system from a graphical user interface.

A typical experiment would proceed as follows:

a) perform PL survey scan (PL intensity vs wavelength) over a user defined spectral range on xy sample grid ~ 50x50 um with 2 um grid spacing to identify regions of interest; create xy heat map of PL intensity and linewidth of selected PL feature(s);

b) software select a grid point and perform high spectral resolution PL scan on selected emission peaks which exhibit very narrow linewidths suggestive of single photon emitters in selected region of interest identified in step a);

c) perform time-resolved PL measurement on selected emission peak, extract lifetime

d) perform antibunching measurements on selected emission peak to determine value of second order autocorrelation function g2(t=0) to determine if feature is a single photon emitter.

I. Confocal Optical Microscope

· Research grade microscope column to view sample with either binocular eyepiece or CCD camera, provide laser excitation to sample, and collect / transmit sample luminescence to detector system with diffraction limited spatial resolution

· Polarization preserving optical path to sample and detectors

· Interchangeable objective lenses to include 20x, 40x or 50x, and 100x, or similar magnifications (3 lenses total)

· Manual sample positioning stage with 1” by 1” range and 1 um resolution

· Scanned objective lens or galvo mirror scanned beam for sample imaging / scanning in the sample plane (xy)

· Scan range 80x80 microns at 20x magnification

· Scan resolution 10nm

· Interfaced to data acquisition software for automated scanning and intensity / lifetime mapping in the xy plane

· Capable of interfacing with a commercially available closed cycle optical cryostat to provide controlled sample temperature over the range of 10-300 K with a working distance of 3 mm or less (cryostat NOT included in this request

· Example cryostat: Montana Instruments Cryostation)

· Capable of interfacing with at least one commercially available atomic force microscope to offer tip-enhanced luminescence (NOT included in this request)

II. Pulsed diode lasers and power supplies for optical excitation of sample

· Set of pulsed diode lasers providing software selection of wavelength and power

· Laser driver / power supply providing temperature stabilized operation and control in both pulsed and cw modes

· Wavelengths to include 532 ± 1 nm, 640 ± 10 nm, 730 ± 10 nm

· Each wavelength includes clean-up filter, collimator, dichroic filter and bandpass filters

· Pulse width < 100 ps

· Rep rate of 40-80 MHz

· Minimum average pulsed power of at least 2 mW, CW power of at least 10 mW

· Polarization preserving optical path to sample

· User selectable linear / circular polarization

· User selectable neutral density filters or equivalent to control laser intensity at sample

III. TRPL using tunable narrow bandpass filter (note that this can use one leg of the HBT detection path described in the next section)

· Capable of less than 100 ps time resolution after deconvolution with instrument response function (IRF)

· Spectral analysis shall be performed with a narrow bandpass filter centered at 750 nm, with center wavelength and bandpass controlled by user

· Bandpass selectable from 3 to 12 nm

· Center wavelength selectable from 700 ± 10 nm to 800 ±10 nm

· Transmission greater than 50%

· Photodetector shall have the following characteristics

· Spectral range 400-950nm

· Quantum efficiency >65% at 750nm, and 20% at 950nm

· Response time < 250 ps

· Dark count rate < 100 per sec

· Dead time < 30 ns

· All control and analysis software to record, analyze and present lifetime data, including dynamic deconvolution of IRF

· Stage must provide at least one unused free space exit port

IV. Single photon antibunching measurement using tunable narrow bandpass filter

· Utilize Hanbury-Brown-Twiss (HBT) methodology with 2 matched photodectors

· Utilize time correlated single photon counting (TCSPC) technology

· Capable of 100 ps or less time resolution after deconvolution with instrument response function (IRF)

· Stage must provide at least one unused free space exit port

· Spectral analysis shall be performed with a narrow bandpass filter centered at 750 nm, with center wavelength and bandpass adjustable by user

· Bandpass selectable from 3 to 12 nm

· Center wavelength selectable from 700 ± 10 nm to 800 ±10 nm

· Transmission greater than 50%

· Photodetectors shall have the following characteristics

· Spectral range 400-950nm

· Quantum efficiency >65% at 750nm, and 20% at 950nm

· Response time < 250 ps

· Dark count rate < 100 per sec

· Dead time < 30 ns

· All control and analysis software to record, analyze and present antibunching data, including dynamic deconvolution of IRF

· Analyze and graphically present second order autocorrelation function g2(t), extract lifetime and g2(0) for CW laser excitation

· Analyze and graphically present intensity correlation data for pulsed laser excitation to extract g2(0)

V. Stage for High resolution PL survey and time resolved photoluminescence analysis

· Provides wavelength analysis of steady state emission for survey scans over a wide wavelength range of 400-900 nm

· Provides time resolved analysis of emission lifetime at a user specified wavelength

· This stage can be fiber coupled to the light collecting optics

· Spectral analysis shall be performed with a grating spectrometer

· Includes at least two user selectable gratings providing spectral resolution of 1nm or smaller, with center wavelengths of approximately 700nm and 850nm

· Grating and slit widths are adjustable by user

· Spectrometer shall include two internally cooled user selectable photodetectors optimized for different wavelength ranges and temporal response times

· Detector 1: 400-800 nm with quantum efficiency (QE) > 20% at 500 nm and response time of ~150 ps or less, providing effective temporal resolution of < 50 ps after deconvolution of IRF

· Detector 2: 400-900 nm with QE > 10% at 850 nm and response time of ~150 ps or less, providing effective temporal resolution of < 50 ps

· All control and analysis software to record, analyze and present PL survey scan and time resolved data, including dynamic deconvolution of IRF

· Analyze and graphically present PL survey scan data

· Analyze and graphically present time resolved emission data and lifetimes

VI. Software, electronics, time correlated single photon counting control

· time-correlated single photon counting electronics with time resolution of 5ps or less

· independently operate all detectors listed without mechanically reconfiguring electrical connections,

· all electronics and power supplies for lasers and other system components

· control computer and monitor at least 32” diagonal or greater

· control and analysis software necessary to operate system from a graphical user interface

· control of all data acquisition parameters

· analysis of data including fitting and extraction of lifetimes

VII. Demonstrated measurement capability The vendor shall provide evidence that their system can measure the PL emission from these monolayer materials by submitting a PL spectrum obtained with their instrument from a monolayer of MoSe2, and from a monolayer of WS2 at room temperature with a signal to noise ratio > 10, together with the acquisition parameters (laser power at sample, dwell time, etc). NRL will supply the monolayer samples.

OPTIONAL ITEMS

Please quote the following as optional line items

1. addition pulsed lasers, minimum average pulsed power of at least 2 mW, CW power of at least 10 mW, pulse width < 80ps, at wavelengths of

a) 594 nm

b) 705 nm