![]() The best-known and most widely used He-Ne laser operates at a wavelength of. Polychromatic source: A light source which consist of several spectral lines of various wavelengths. A heliumneon laser or He-Ne laser, is a type of gas laser whose high energetic medium gain medium consists of a mixture of ratio (between 5:1 and 20:1) of helium and neon at a total pressure of about 1 torr inside of a small electrical discharge. Conventional FBGs fabricated by using an ultraviolet (UV) laser phase-mask method require the sensitization of the optical fiber and could not be used at high temperatures. Example: Helium-Neon laser beam which emits light in red part of the visible spectrum. Fiber Bragg grating (FBG) is the most widely used optical fiber sensor due to its compact size, high sensitivity, and easiness for multiplexing. Monochromatic source: A light source which consists of only one single wavelength (spectral line). In this paper, as the first step of research, a prototype optical setup with a mode-locked femtosecond laser source is developed, and some basic experiments are carried out to demonstrate the feasibility of proposed method. l distance between grating and the screen. By utilizing the number of Littrow angles obtained from the multiple diffracted beams in the same diffraction order, highly accurate measurement of the grating period can be expected. Examine the set up in the 3D window, it shows a laser, a diffraction grating, and a screen. The first-order diffracted beam provides optical feedback to the laser diode chip, which has an anti-reflection coating on the right-hand side. The common Littrow configuration (see Figure 2a) contains a collimating lens and a diffraction grating as the end mirror. First, 2 g changes sign on the opposite sides of the stop band centered at the Bragg wavelength, whose location is easily controlled and can be in any region of the optical spectrum. Since the optical modes in a mode-locked laser, which are often referred to as the optical frequency comb, have deterministic mode frequencies with equal intervals in frequency domain, multiple diffracted beams in the same diffraction order can be obtained. This is a simulation of a typical laser diffraction lab set up. They are also called grating-stabilized diode lasers. The dispersive properties of a fiber grating are quite different from those of a uniform fiber. ![]() We propose, in particular, to measure the pitch of the grating through the measurement of the diffraction produced on the He-Ne laser beam. The proposed method is established in such a way that a mode-locked femtosecond laser beam is employed as a light source for the traditional laser diffraction method, in which the Littrow configuration is utilized to evaluate grating period. With the new Laser He-Ne (described in the Laser He-Ne post), you can easily test the physical properties of the diffraction grating. This paper presents a newly proposed method referred to as the femtosecond laser diffraction method for measurement of the grating period.
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