Raman Spectrometer 532/785/1064nm
Standard Spectrometer 200-1100nm
High Sensitivity UV Enhanced Spectrometer
BSI Cooled High Sensitivity Spectrometers
Large NA High QE Spectrometer 200-1450nm
Near Infrared Spectrometer 900-2500nm
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Auto-Fluorescence Microscope
Confocal Raman Microscope
Spinning Disk Confocal Microscope
Industry Line Scan Confocal Microscope
Research Line Scan Confocal Microscope
Laser Point Scanning Confocal Microscope
TCSPC System for SPAD (APD) Testing
Maskless Lithography UV Laser Writer
Laser Doppler Vibrometer 0.1Hz to 5Mhz
OCT Imaging System
X-ray/XRD Heating & Cryo Stage
Optical Heating & Cryo Stage
Electrical Probe Temperature Stage
Adjustable Electrical Probe Station
Tensile Strain Temperature Stage
Fiber Spectrometers (200nm to 5um)
X-Ray/XUV/VUV Spectrometers (1-300nm)
FT Infrared Spectrometer(900-16000nm)
Hyperspectral Camera (220nm-4.2μm)
Multi-Spectral Camera (400-1000nm)
Silicon photomultiplier(SIPM)(300-950nm)
Single Photon Detector (SPD)(200-1700nm)
Photomultiplier Tubes (PMT)(160-900nm)
Photodiode Detector (PD) (200nm-12um)
Pyroelectric Infrared Detectors (2-12um)
Single-Photon Avalanche Diode Array
UV-VIS Beam Profiler(190-1100nm)
VIS-NIR Beam Profiler(350-1750nm)
Mid-infrared Beam Profiler(2-16μm)
Compact Beam Profiler(190-1100nm)
Terahertz Beam Profiler
Scanning Slit Beam Profiler
Photodiode Power Sensors 250-2500nm
Power Meter Console
Integrating Spheres (10mm-100mm)
Power Meter Adaptor & Accessories
Thermoelectric laser power meter(0.19-25 μm)
Photoelectric power meter(200-1100nm)
VUV/UV Spectrograph
Standard Single Grating Monochromator
Hi-Res Single Grating Monochromator
Double Grating Scanning Monochromator
Triple Grating Scanning Monochromator
Hi-Res Triple Grating Monochromator
LIV Test Systems for Laser Diode / LED
White Light Interferometer
Optical Coating CRD Reflectrometer
Optical Test Measurement System
RF Test Measurement System
Point confocal displacement sensor
Linear confocal displacement sensor
CW Pigtail Laser Diode (400-1920nm)
CW Laser Diode Module (375-785nm)
CW Multi-Channel Lasers (405-640 nm)
CW Narrow Linewidth Diode Laser
Nanosecond Pulsed Laser (266nm-3.4μm)
DFB/FP Picosecond Laser (370-1550nm)
Nanosecond Pulse Fiber Laser(1064-2μm)
Picosecond Pulse Fiber Laser (266nm-2μm)
Femtosecond Pulse Fiber Laser (515nm-2μm)
CW & QCW Fiber Laser System (405nm-2μm)
CW Narrow Linewidth Laser(780nm-2μm)
C-Band Tunable Laser (1529 -1567nm)
L-Band Tunable Laser (1554 -1607nm)
Supercontinuum Fiber Lasers 450-2300nm
2 μm CW Wide Tunable Laser (1900-2000 nm)
Mid-infrared Wide Tunable Laser (4-12 μm)
Femtosecond OPA (650 - 2600nm)
Erbium Doped Fiber Amplifier
Ytterbium Doped Fiber Amplifier
Thulium-Doped Fiber Amplifier
Semiconductor Optical Amplifier
Fiber Raman Amplifier
EUV Light Sources(58-130nm)
VUV Light Sources(115-400nm)
ASE Light Sources (830-2000nm)
Microscopy Imaging LED Sources 360-780nm
Collimated LED Sources (240-980nm)
Fiber-Coupled LED Sources (265-940 nm)
Standardized Repetition Locking Optical Combs
Fully Locked Optical Frequency Combs
Asynchronous Optical Sampling Light Source
Optical Frequency Comb Accessories
Light Field Sythesizer
Hollow-Core Fiber Compressor
High Powered Hollow-Core Fiber Compressor
Ultra-High Contrast 3rd-Order Autocorrelator
Coherent Ultrabroadband XUV Light Source
Enhanced Cavities for Laser Light
Terahertz Quantum Cascade Lasers(1-4.5Thz)
MIR QCL Turn-Key System (3-13μm)
MIR Packaged QCL(4-9.7μm)
MIR QCL Chips(4-12μm, Package Customizable)
Fluorescence Upright / Inverted Microscope
Biological Upright / Inverted Microscope
Phase Contrast Microscope
Dark Field Microscope
Polarizing Microscope
Metallographic Upright / Inverted Microscope
Smart 3D Stereo Microscope
USB Digital Microscope With Platform
Built-in Digital Microscope
Plan Apochromatic Objective
Industrial Plan Objective
Biology Plan Objective
Microscope CCD Camera (VIS-NIR)
Microscope CMOS Camera (UV-NIR)
UV & NIR Enhanced CMOS Camera
Hyperspectral Camera for Microscope
Multispectral Camera For Microscope
Microscope Light & Lamp
Soft X-Ray BSI sCMOS Camera (80-1000eV)
High-Speed sCMOS Camera
High Sensitivity sCMOS Camera
38M Pixel large Format sCMOS Camera
Compact BSI/FSI sCMOS Camera
Intensified CMOS Camera (200-1100nm)
Full Frame CCD Camera for UV VIS NIR
Full Frame CCD Camera for VUV EUV X-ray
Full Frame In-vacuum CCD Cameras
Large Format In-vacuum CCD Cameras
HDMI Color CMOS Camera (Monitor)
High Speed Line Scan Camera
Large Format Camera
High Speed Large Format Camera
Frame Grabber
Infrared Pyrometers (-40-3000C)
Linear Array Infrared Thermal Imager
Matrix Array Infrared Thermal Imager
Blackbody Calibration Sources -15 to 1500°C
Short-Wave Infrared Camera (SWIR)
Mid-Wave Infrared Camera (MWIR)
Long-Wave Infrared Camera (LWIR)
Solar Blind UV Imaging Module 240-280nm
UV-VIS Online Monitoring Module
UV-VIS Dual Channel Camera
UV-VIS-IR Triple Spectral Fusion Camera
Ultraviolet Camera for Drone
Free Space Acousto-Optic Modulators (AOM)
Fiber Coupled Acousto-Optic Modulators
Free Space Acousto-Optic Tunable Filter
Fiber-coupled Acousto-optic Tunable Filter
Acousto-Optic Q-switch (AOQ)
Acousto-Optic Frequency Shift (AOFS)
Electro-optical Amplitude Modulator
Electro-optic Phase Modulator
Ultra-fast Pulse Generator for TCSPC
Single-photon time counter
Phase Spatial Light Modulator
Transmission Amplitude SLM
Reflection Amplitude SLM
Digital Micromirror SLM
Pulsed Voltage
Pulsed Current
General Purpose Pulse Generators
Medium and High Voltage Pulse Generators
High Speed Impulse Generator
Very High Speed Pulse Generators
Function Generators
Pulse Amplifiers
Single-channel Lock-in Amplifier
Dual-channel Lock-in Amplifier
TPX / HDPE Terahertz Plano Convex Lens
Off-Axis Parabolic Mirrors
Terahertz Hollow Retro Reflector
Terahertz Metallic Mirrors
ZnTe / GaSe Terahertz Crystals
Terahertz Beam Expander Reflection
Waveplates
Optical Isolator
Optical Polarizers
Beamsplitter Plate
Beamsplitter Cube
Dichroic Beamsplitters
Ultrathin Beamsplitter Plate
Bandpass Filters Fluorescence Microscope
Filters for Raman Spectroscopy
Narrow Filters for Laser
Filters for FISH
Filters for TIRF Microscope
Filters for FRET Microscope
Laser Crystals
Nonlinear Optical Crystals
Birefringent Crystals
Optical Crystals
Electro-optical Crystals
Micro-Channel Plate (MCP)
Micro-Channel Plate Assembly (MCP)
Fiber Optic Plates (FOP)
Micro Pore Optics
X-Ray Collimators
Hybrid Fiber Components
Electrically Adjustable Optical Delay Line
Manually Adjustable Optic Delay Line
Optical Circulator
Filter Coupler
FA Lens
Zoom Lens
Telecentric Lens Series
In-situ Tensile Heating & Cryo Stage
Live-Cell Incubator Stages
Single Axis Motorized Piezo Stage
XY Motorized Piezo Stages
Multi Axis Motorized Piezo Stages
Vacuum Non-magnetic Piezo Stage
Nano Electric Actuator
XY Stepper Motor Stages
XYZ 3 Axis Stepper Motor Stages
XY Microscope Piezo Stages
XY Microscope Linear Motor Stages
Motorized Filter Wheel
FWR Motorized filter wheels
13mm Linear Stages
25mm Linear Stages
Rotation and Tilt Stages
Rack and Pinion Stages
Vertical Axis Stages
2-Axis Stages
Solid Vibration Isolation Optical Table
Solid Vibration Isolation Table
Pneumatic Optical table
Pneumatic Optical Table With Pendulum Rod
Honeycomb Optical Breadboard
Lens Mounts
Mirror Mounts
Filter Mounts
Permanentely aligned interferometer
The heart of the FT-Rocket is dual corner-cube (retro-reflector) interferometer. The two corner-cubes are fixed to a common swinging arm, which rotates to create an optical path difference (with respect to the beam splitter) in the two arms of the interferometer.
This type of design is called a permanently aligned interferometer. This particular arrangement of the interfeormeter is known to be the most robust against vibrations and temperature drifts. It never has to be realigned. The swinging arm of the interferometer rotates on wear-free flexure system, making this mechanical system extremely robust and durable.
Solid-state reference laser
For measuring the movement of the mirrors, a solid-state reference laser is coupled into the interferometer. Compared to classic HeNe lasers, the solid-state lasers that we use are more compact and have a much longer life-time. They have a very low temperature-induced wavelegnth drift and, when kept at constant temperature with a Peltier element, their wavelength can be stabilized to a few PPM, thus providing a very accurate and reproducible wavelength scale. This is crucial for ensuring a day-to-day and unit-to-unit consistency.
Introduction
Fourier Transform infrared (FT-IR) spectrometers have proven to be efficient and reliable tools for a large variety of applications targeting the near infrared (NIR) and mid-infrared (MIR) regions of the electromagnetic spectrum. One of the most critical specification of FT-IR spectrometers is their spectral resolution , as this defines the scale of the features to be distinguished e.g. in the absorbance spectrum of a gas. It is thus quite natural to wish for the highest achievable resolution when purchasing an FT-IR spectrometer. Due to their operational mode, achieving high resolution measurements using FT-IR spectrometers is however not entirely straightforward. This technical note explains the main limits of high resolution FT-IR measurements.
A simplified FT-IR is depicted in Fig.1. It consists of a beamsplitter, a fixed mirror and a movable mirror. Light from a purely monochromatic light source is split in two beams, assumedly in equal parts (50% beamsplitter). Each beam bounces back on either mirror (fixed or movable) before being recombined and focused onto the detector. When the movable mirror is at the same distance from the beamsplitter as the fixed mirror, both beams travel the same distance and recombine in-phase, yielding constructive interference. By displacing the moving mirror by a distance ℓ, one introduces an optical path difference (OPD) between the two beams Δ given by:Δ=2ℓ.
Upon recombination at the detector, the optical intensity as a function of OPD is given by: I(0)=0.5I0[1+cos(2πν0∆)]=IDC+IAC(∆).
Where I0 is the source intensity at wavenumber ν0 (the wavenumber is the reciprocal of the wavelength). The AC part of the interference record is labelled IAC(Δ) and is called the interferogram. For a purely monochromatic source (as considered here), the interferogram is a pure cosine function.
Fig 2. Interferogram of a purely monochromatic light source
Here the wavenumber (or equivalently the wavelength) of the source as well as its intensity can be retrieved from a direct observation of the interferogram (amplitude and period of the cosine function). For a broadband source, the interferogram IAC(Δ) and spectrum I0(ν) of the source are related via a Fourier transform operation:
I0(v)=∫∆maxIAC(∆)cos(2πν0∆)d∆
Obviously, the OPD cannot be made arbitrarily large and has to reach a value Δmax that is defined by technological design. Given the nature of the relationship between the interferogram and the spectrum (Fourier transform), it turns out that Δmax also defines the achievable spectral resolution. To a first approximation, the spectral resolution Δν of an FT-IR is given by:
∆ν=(∆max)-1
and is often expressed in cm-1. So why not simply increase the maximum OPD to enhance the spatial resolution of an instrument ? While this is true, special care has to be considered when operating at high resolution. As explained hereafter, the mirror maximum displacement is limited by the divergence of the system and the dimensions of the detector.
We consider the exact same setup as in Fig.1. The beam divergence is accounted for by observing the behavior of the so called "extreme ray", which makes an angle α with respect to the "central ray" discussed previously.
Fig 3. FT-IR setup with a divergent source
The two extreme rays (reflected from either the fixed or the moving mirror) hit the lens with an angle α, unlike the central ray which hits the lens at normal incidence. They are thus focused on another point on the detector. Moreover, their OPD is shorter than for the central ray:
∆ext=2ℓcos(α)
The larger the angle α, the greater the difference with the central ray OPD Δcen=2ℓ. Consider now the case where the difference in OPD between the central ray and the extreme ray is equal to one half of the source wavelength, that is:
∆cen-∆ext=2ℓ[1-cos(α)]=λ/2
In this scenario, when the central rays are in phase, then the extreme rays are out of phase (and vice versa). Consequently, the intensity over the detector surface follows the profile shown in Fig. 4.
Fig 4. Intensity over the detector surface due to a highly diverging beam
Since the detector yields a single value that corresponds to the average intensity received on its surface, the signal detected in this case corresponds to the average optical intensity only, and all information regarding the interference signal vanishes. Practically speaking, the interferogram will start losing contrast as the moving mirror is scanned as shown in Fig. 5.
Fig 5. Loss in interferogram contrast due to a diverging beam
This effect is naturally existing in all interferometers based instruments (such as FT-IR) and cannot be avoided. It can however be properly managed by appropriately trading-off the parameters involved in equation (6), namely :
For most applications in solids and liquids, the size of the observable features is typically broader than 2cm-1, and high resolution (HR) measurements performed at 0.5cm-1 are usually not required. In addition, these would prove challenging due to the added contrast loss described in this document. HR measurements might still be a viable option for specific applications, such as e.g. laser characterization, where the highly collimated laser beam prevents the dramatic loss of the interferogram contrast.
We fully appreciate and value the multiple benefits that a dedicated, performant and reliable software can bring to your application. Automatic data collection, parameters changes, status diagnosis and many other essential tasks should be implemented as simply and as efficiently as possible in order to get the most out of your spectrometer. This philosophy led to the development of a multi-threading, cross-platform and versatile software application, the digital acquisition system or AoDAQ.
The AoDAQ simultaneously takes care of:
1. Handling communication with the FT-IR via USB
2. Processing raw signals to deliver a spectrum
3. Running a TCP Ethernet server
The AoDAQ can be installed on all sorts of computers, from desktop machines to embedded, low-power single board computers. Thanks to the hosting of a TCP server, the instrument data and parameters can be accessed locally and/or remotely. All communication with the instrument eventually reduces to a set of TCP/IP commands that allow to quickly acquire data, adjust parameters, monitor the instrument status etc. using the programming environment of your choice.
1.What resolution should I use for my application?
In FTIR, resolution is traded-off with two other experimental metrics that are acquisition time and signal-to-noise ratio (SNR). Increasing resolution, meaning reducing the resolution parameter number, will result in longer acquisition time, and poorer SNR. In general, it is recommended to work at the "worst" possible resolution, that is the limit resolution that allows to distinguish the features of the sample or substance that you are characterizing. Liquids and solids present broader features than gases or gas mixtures and can generally be probed with standard resolution instruments (down to 2cm-1). Gas analysis or light sources characterization (typically lasers) usually benefit from a sharper resolution of 0.5cm-1.
2.How is the equivalent wavelength resolution calculated?
Due to its working principle, FT-IR provides uniformly sampled spectra in the form of wavenumber (ν) within a given spectral range, with the unit of cm-1. Wavenumber is simply defined as the reciprocal of wavelength (λ). The resolution of a FT-IR is a constant wavenumber (Δν), but varies with the wavelength (Δ λ) due to the inverse relationship between these two units. The conversion between wavenumbers resolution and wavelengths resolution is Δλ=λ2 · Δν, as shown in the following figure:
3.What is the acquisition rate of this spectrometer?
The acquisition rate varies with the resolution. At the standard resolution of (4cm-1), the scanning rate is ~5Hz, and at the high resolution of (0.5cm-1), the scanning rate is ~1Hz, that is, the scanning rate is inversely proportional to the resolution.
4.What are the differences between DLADTGS detectors and MCT detectors?
DLADTGS is based on the pyroelectric effect. When exposed to infrared radiation, its temperature will change, causing the polarization inside the crystal to change. MCT is a bandgap type photoconductive detector. DLADTGS has a wider spectral response range (up to 18-20 μm), and MCT detectors utilize thermoelectric cooling to achieve higher sensitivity, which can suppress dark current and improve their signal-to-noise ratio.
5.How much better is the performance of LN4 cooled detectors than that of MCT cooled detectors?
The SNR of the LN4 cooling system is approximately ten times that of the MCT cooling system.
6.Why is the performance of the Fourier transform spectrometer superior to that of the dispersive grating spectrometer?
The performance of a grating spectrometer mainly depends on the slit and detector. Due to the different dark noise of each pixel point, additional noise will be introduced during measurement. FTIR spectrometers are generally superior to dispersive grating spectrometers due to their higher light throughput, better signal-to-noise ratio, higher spectral resolution and wider wavelength range. These advantages make FTIR spectrometers the preferred choice in many applications, especially in places where high sensitivity and accuracy are required.
7.Can an FTIR spectrometer be used to measure pulsed laser?
Sure, but the power of the laser must be limited to avoid irreversible damage to the detector. The average power shall not exceed 25mW, and the peak power of pulses shorter than 1µs shall not exceed 100W. It is recommended to use a set of fixed or variable attenuators to adjust the optical power to avoid detector saturation. Secondly, the repetition frequency of the laser must exceed 25khz to avoid numerical artifacts (aliasing) in the measured spectrum.
8.Can the concentration of the substance being measured be obtained directly?
No. A spectrometer can only provide the measured spectrum. Users must obtain the concentration of substances in the sample through specific algorithms and calibration data.
9.Can this spectrometer be used for mineral identification?
The FT-NIR spectrometer is highly suitable for mineral identification. FT-NIR is capable of generating high-quality and high-resolution (better than 1nm) reflection spectra within the spectral range of 900-2550nm (SWIR) within a few seconds.
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