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IR Spectrometers

IR Spectrometers

There are two main infrared (IR) spectrophotometers: dispersive IR spectrometers and Fourier transform infrared (FTIR) spectrometers. In a dispersive IR spectrometer, a beam of infrared radiation produced by a hot wire is divided into two parallel equal-intensity beams using mirrors. One beam passes through the sample, while another is a reference beam. The beams then move through the monochromator, which separates the radiations into a continuous spectrum of different frequencies. The...

IR Frequency Region: Fingerprint Region

IR Frequency Region: Fingerprint Region

IR spectra are divided into two main regions: the diagnostic region and the fingerprint region. The diagnostic region of the spectrum lies above 1500 cm−1. The absorptions resulting from single-bond vibrations of the N–H, C–H, and O–H stretch at higher wavenumbers and appear on the left side of the spectrum. The stretching absorptions of the C≡C and C≡N occur between 2100–2300 cm−1. In contrast, those arising from stretching absorptions of the C=O, C=N, and C=C occur between 1600–1850 cm−1.
The...

IR Frequency Region: X–H Stretching

IR Frequency Region: X–H Stretching

In IR spectroscopy, signals produced by the X−H bonds (such as C−H, O−H, or N−H) can be observed in the frequency range of 2700–4000 cm–1. The C−H stretching vibration forms sharp bands in the region 2850–3000 cm–1. The presence of the O−H stretching vibration leads to the forming of an absorption band in the frequency range 3650–3200 cm−1. At the same time, N−H stretching can be confirmed by absorption bands in the 3500–3100 cm−1 range. Even though both O−H and N−H bonds vibrate at a similar...

IR Absorption Frequency: Hybridization

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Hydrocarbons such as alkanes, alkenes, and alkynes show characteristic C–H stretching absorption bands. These IR stretching frequencies depend on the hybridization of the involved carbon atom and can be explained in terms of the s character of each hybridized atomic orbital.
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Infrared (IR) Spectroscopy: Overview

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When electromagnetic radiation passes through a material, atoms or molecules transition from a lower to a higher energy state by absorbing radiation corresponding to the energy difference between the two states. The absorption of infrared (IR) radiation causes transitions between vibrational energy levels in a molecule. Therefore, IR spectroscopy is a useful analytical tool for determining the molecular structure of molecules.
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IR Spectroscopy: Molecular Vibration Overview

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When Infrared (IR) radiation passes through a covalently bonded molecule, the bonds transition from lower to higher vibrational levels. The fundamental vibrational motions that result in infrared absorption can be classified as stretching or bending vibrations.
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Related Experiment Video

Updated: May 21, 2026

Generation and Coherent Control of Pulsed Quantum Frequency Combs

Generation and Coherent Control of Pulsed Quantum Frequency Combs

Published on: June 8, 2018

Widely-tunable mid-infrared frequency comb source based on difference frequency generation.

Axel Ruehl¹, Alessio Gambetta, Ingmar Hartl

¹LaserLaB Amsterdam, VU University Amsterdam, de Boelelaan 1081, 1081 HV Amsterdam, The Netherlands.

|June 29, 2012

Summary

This summary is machine-generated.

We developed a tunable mid-infrared frequency comb covering the 3-10 μm molecular fingerprint region. This breakthrough enables broader molecular spectroscopy applications with high power output.

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Area of Science:

Optics and Photonics
Spectroscopy
Materials Science

Background:

Mid-infrared (mid-IR) light sources are crucial for molecular spectroscopy.
Existing sources often lack broad tunability across the molecular fingerprint region (3-10 μm).
Frequency combs offer precise wavelength control but extending them to the mid-IR is challenging.

Purpose of the Study:

To demonstrate a highly tunable mid-IR frequency comb source.
To cover the entire 3-10 μm molecular fingerprint region.
To achieve significant output power for spectroscopic applications.

Main Methods:

Difference frequency generation (DFG) in a Gallium Selenide (GaSe) crystal.
Pumping the DFG process with a 151 MHz Ytterbium-fiber (Yb:fiber) frequency comb.
Seeding the DFG with Raman-shifted solitons generated in a nonlinear suspended-core fiber.

Main Results:

Achieved unprecedented tunability across the entire 3-10 μm spectral range.
Generated average output powers up to 1.5 mW at 4.7 μm.
Demonstrated a robust system based on DFG and nonlinear fiber optics.

Conclusions:

The developed mid-IR frequency comb source significantly advances molecular spectroscopy capabilities.
The broad spectral coverage and power output open new avenues for chemical analysis and sensing.
This work highlights the potential of nonlinear fiber optics and DFG for generating versatile mid-IR light.