FT-NIR / FT-IR

Hamamatsu products for FT-NIR / FT-IR
FTIR engines (for FT-NIR)
Type II superlattice infrared detector (for FT-IR)
Related documents

FTIR (Fourier Transform Infrared Spectroscopy) is a method of infrared spectroscopy. A sample (solid, liquid, or gas) is irradiated with infrared light, the transmitted or reflected light is interfered with by an interferometer, and spectral information is acquired by Fourier transforming the signal intensity.

Since qualitative, quantitative, and identification of substances are possible from the obtained spectral information, analyzers and spectrophotometers using FTIR are used in a wide range of fields, including medical, chemical, environmental, and material analysis. Depending on the wavelength range of infrared light handled, they are sometimes distinguished as FT-NIR (near-infrared light) or FT-IR (mid-infrared light).

Hamamatsu products for FT-NIR / FT-IR

Wavelength (μm)	FT-NIR		FT-IR
Wavelength (μm)	1	2	5	10	15
Spectrometers	FTIR engines (1.1 ～ 2.5 μm)
Infrared detectors	InGaAs photodiodes (1 ～ 2.5 μm)
	InAs photovoltaic detectors (1 ～ 3.8 μm)
	InSb photovoltaic detectors (1 ～ 5.5 μm)
	InAsSb photovoltaic detectors (1 ～ 11. μm)
	Type II superlattice infrared detectors (1 ～ 14.5 μm)

FTIR engines (for FT-NIR)

The FTIR engine (FT-NIR spectrometer) is a compact Fourier transform infrared spectroscopy module that combines a Michelson optical interferometer and control circuit in a palm-sized housing. We have made our FTIR engine more compact while retaining the features of the Fourier transform type by applying our unique MEMS technology and mounting technology to the optical interferometer.

FTIR engine C15511-01

FTIR engine C16511-01

Features

High detection performance

To eliminate the decrease in incident light level caused by miniaturization, we used Hamamatsu original MEMS technology to develop a movable mirror that composes the actuator inside the optical interferometer, then improved upon it so that the reflected light can be used efficiently. Furthermore, we integrated the movable mirror and the fixed mirror as a MEMS chip, thereby making it compact and reducing error in the relative angle between the mirrors to about 1/100. By optimizing the structure and drive method of the MEMS actuator and eliminating blurring when in operation, we have suppressed the spread of infrared light inside the optical interferometer and reduced loss. By doing so, we have realized detection performance comparable to conventional stationary type devices.

High wavelength reproducibility

Optical interference occurs when the light being measured (incident light) is split by a beam splitter, reflected by the movable mirror and fixed mirror, then combined again. Interference light intensity, which changes depending on the position of the movable mirror, is detected by a photodetector (InGaAs PIN photodiode), then the signal is subjected to arithmetic processing (Fourier transform) to obtain the optical spectrum. By measuring the position of the movable mirror inside the interferometer using a photodetector (Si PIN photodiode) and semiconductor laser (VCSEL), it is possible to obtain an optical spectrum with high wavelength reproducibility.

Compactness and high accuracy

Figure: Optical system of FTIR engine

Measurement examples

The near-infrared region from 1.1 μm to 2.5 μm is used for infrared spectroscopic analysis in various fields because many materials have unique absorption spectra in this region. There are two types of infrared spectral analysis using FTIR engines: reflection measurement and transmission measurement.

Reflection measurment (sugar)

Comparing the reflection measurement results of sugar powder samples from the FTIR engine and from a stationary spectrometer, we found it was possible to accurately measure even minute peak patterns with the FTIR engine, similar to spectra obtained with the stationary spectrometer.

Transmittance measurement (alcohols)

We were able to obtain the characteristic spectrum in the absorption bands of water and alcoholic beverages. In addition, with the results of estimating the alcohol concentration from absorbance in the 2.3 µm band, we confirmed that the estimated values and numerical values of components contained in the beverage matched, and that high accuracy measurement is possible.

Type II superlattice infrared detector (for FT-IR)

Many of the mid-infrared photodetectors used in FTIR contain substances restricted by the RoHS Directive, so there has been a need to develop alternative products. As a compound opto-semiconductor device capable of detecting up to 14.5 μm, we have succeeded in mass-producing the world's first Type II superlattice infrared detector without using substances restricted by the RoHS Directive (mercury and cadmium). Modules with a preamplifier that can be operated simply by connecting a DC power supply are also available.

Type II superlattice infrared detector P15409-901

InSb photovoltaic detectors

Features

Detectable up to 14.5 μm

Excellent output linearity

Mass production enabled

Unlike typical opto-semiconductors, the main feature of this product is the “superlattice” structure in which thin films of InAs and GaSb compounds, each with a thickness of several nanometers, are alternately stacked to more than 2000 layers. Mass production was achieved by precisely controlling the amount and timing of stacking InAs and GaSb to the substrate using Hamamatsu’s unique compound semiconductor technology and optimizing temperature, pressure, and other conditions to establish a manufacturing method.