Interferometer, diagram

The schematic interferometer diagrams given do not show most of the optics, such as beam collimators and focusing mirrors. Mirrors in an FTIR are generally made of metal. The mirrors are polished on the front surface and may be gold-coated to improve corrosion resistance. Commercial FTlRs use a variety of flat and curved mirrors to move light within the spectrometer, to focus the source onto the beam splitter, and to focus light from the sample onto the detector. 

Figure 2. Diagram of the atomic Sagnac interferometer at Yale (Gustavson et al., 2000). Individual signals from the outputs of the two interferometers (gray lines), and difference of the two signals corresponding to a pure rotation signal (black line) versus rotation rate.

A diagram of a typical interferometer (Michelson type) is shown in Figure 7.8. It consists of fixed and moving front-surface plane mirrors (A and B) and a beamsplitter. Collimated infrared radiation from the source incident on the beamsplitter is divided into two beams of equal intensity that pass to the fixed and moving mirrors respectively. Each is reflected back on itself, recombining at the beamsplitter from where they are directed through the sample compartment and onto the detector. Small... 

Fig. 5.20. (Top) Schematic diagram of a Michaelson interferometer. Retardation determines difference in optical path between fixed mirror and moving mirror. When retardation, S, is 1/2 light with a wavelength equal to A will be reinforced. (Bottom) Interference pattern from the Michaelson interferometer. Major peak where S = 0 is where all wavelengths are reinforced.

Figure 4.5 Schematic diagram of a Fourier transform infrared (FTIR) spectrometer. Infrared radiation enters from the left and strikes a beam-splitting mirror (BS) angled such that half of the beam is directed towards a fixed mirror (Mi) and half towards a moveable mirror (M2). On reflection the beam is recombined and directed through the sample towards the detector. M2 is moved in and out by fractions of a wavelength creating a phase difference between the two beam paths. This type of device is called a Michelson interferometer.

Figure 6. Schematic diagram of an interferometer as used in FTIR instruments.

Figure 21. Schematic diagram of (a) an evanescent field sensor, and (b) a simple waveguide circuit where the sensor is incorporated into a Mach-Zehnder interferometer.

Figure 3.22 — (A) Scheme of the Mach-Zehnder interferometer/enthalpimeter. (Reproduced from [152] with permission of Elsevier Science Publishers). (B) Cross-section of polyvinylidene fluoride film-based enthalpimeter. (Reproduced from [156] with permission of the American Chemical Society). (C) Schematic diagram of an enzyme thermistor.

Figure 15.6 is a schematic diagram of an AFM with an optical interferometer (Erlandsson et al., 1988). The lever is driven by a lever oscillator through a piezoelectric transducer. The detected force gradient F is compared with a reference value, to drive the z piezo through a controller. In addition to the vibrating lever method, the direct detection of repulsive atomic force through the deflection of the lever is also demonstrated. 

Figure 18. Schematic diagram of a phase-shift interferometer [from Ref. (56)].

Figure 10.11—Optical arrangement of a Fourier transform IR spectrometer, a) A 90c Michelson interferometer including the details of the beam splitter (expanded view) b) optical diagram of a single beam spectrometer (based on a Nicolet model). A weak intensity HeNe laser (632.8 nm) is used as an internal standard to measure precisely the position of the moving mirror using an interference method (a simple sinusoidal interferogram caused by the laser is produced within the device). According to the Nyquist theorem, at least two points per period are needed to calculate the wavelength within the given spectrum.

Figure 20-26 Schematic diagram of Michelson interferometer. Detector response as a function of retardation (= 2[OM - OS]) is shown for monochromatic incident radiation of wavelength X.

Figure 1. Schematic diagram of the Michelson stop-scan interferometer used for time-resolved FTIR emission studies. Reproduced with permission from Ref. 38.

Figure 9. A schematic diagram of the interferometer used to measure thin film thickness. The inset shows that light is both transmitted and reflected by the thin film. Reproduced from reference [7] with the permission of the Royal Society of Chemistry.

Figure 2. Simplified diagram of the optical layout of the FTIR spectrometer and A are apertures, P and P are polarizers, and the area inside the dashed box the actual interferometer assembly...

A schematic diagram of a Michelson interferometer, the heart of the FTIR system, is shown in Figure 1 (2). The Michelson interferometer modulates each wavelength in the infrared region at a different frequency in the audio range. 

Figure 2-9 Optical diagram of an FT-Raman spectrometer. The heart of the instrument is the interferometer head, consisting of the beam splitter and fixed and moving mirrors.

Block diagram of an interferometer in an FT-IR spectrometer. The light beams reflected from the fixed and moving mirrors are combined to form an interferogram, which passes through the sample to enter the detector. 

Figure 24.14 The left panel is a plan of the testing area near the LENS (reflected shock) tunnel 1 — 8 test section 2 — TDL probe 3 — 4 nozzle M = 8-16 4 — 8" reflected shock tube 5 — fiber optic and signal line conduit 6 — data acquisition and 7 — TDL system optical table. The right panel is a schematic diagram of the setup used to record water-vapor absorption in high-enthalpy flows 1 — InGaAs detectors 2 — tunable diode laser Ai = 1400.74 nm 3 — ring interferometer 4 — tunable diode laser A2 = 1395.69 nm and 5 — HoO reference cell...

Schematic diagram of a Michelson interferometer. The detector signal variation as a result of mirror motion is displayed for the cases of monochromatic and polychromatic sources.

Figure 1. Diagram of a Michelson interferometer. Key l, unmodulated incident beam A, moving mirror B, stationary mirror E, modulated exit beam D, detector MD, mirror drive.

Fig. 10.4 Schematic diagram of an integrated optical Mach-Zehnder interferometer modulator. Reprinted from Donval et al. (2000). Copyright 2000, with permission from Elsevier.

Experimental Techniques. A block diagram of the experimental set-up used for saturated absorption experiments is shown in Figure 1. The argon laser is a commercial 4W tube in a home made cavity. This cavity is made of three Invar rods, decoupled from the tube in order to avoid vibrations. Line selection is made with a prism, and single frequency operation is obtained with a Michel son interferometer. The laser can be frequency locked to a stable Fabry-Perot resonator with a double servo-loop acting on a fast PZT for line narrowing and on a galvo-plate for wide tuna-bility. This results in a linewidth of less than 10 KHz and a continuous tunability of 6 GHz. 

As an example of a modern commercial interferometer, the optical diagram of a Bruker IFS 66, is shown in Fig, 3.4-1. It allows working in the optical range from 40000 to 20 cm (250 nm to 500 im), to exchange different internal and external radiation sources and detectors, and to connect various accessories, such as a Raman module or an infrared or Raman microscope. 

Figure 3.4-1 Optical diagram of a commercial Michelson interferometer for infrared and Raman spectroscopy (Bruker IFS 66 with Raman module FRA 106). CE control electronics, D1/D2 IR detectors, BS beamsplitter, MS mirror scanner, IP input port, S IR source, AC aperture changer, XI — X3 external beams, A aperture for Raman spectroscopy, D detector for Raman spectroscopy, FM Rayleigh filter module, SC sample compartment with illumination optics, L Nd.YAG laser, SP sample position.

---