Dye laser

Simple Illustration of Dye Laser.

1. Contents: DYE LASER Working principle Major components Construction Advantages Disadvantages Applications

2. Dye Laser A laser which uses an organic dye as the lasing medium, usually as a liquid solution. A dye can usually be used for a much wider range of wavelengths. These Lasers were discovered by Sorokin and his colleagues. Q-What is a Dye? A dye is a colored substance which imparts(applies) its color to the material it is being applied.

3. Working Principle It works on the principle of population inversion. Q-What is Population Inversion? To achieve optical amplification it is necessary to create a distribution of atoms such that the population of the upper energy level is greater than that of the lower energy level (i.e. N 2 > N 1). This condition is known as population inversion .

4. Major Required Components Active/Lasing Medium Pumping Source Resonator

5. Active Medium Active medium for dye laser is the organic dye.it is a liquid material. Some of the Organic dyes are  R hodamine 6G (orange, 540–680 nm) also known as Xanthene dye ,  F luorescein  (green, 530–560 nm),  C oumarin  (blue 490–620 nm),  S tilbene  (violet 410–480 nm),  U mbelliferone  (blue, 450–470 nm),  T etracene , malachite green, and others. Most Commonly used is Rhodamine 6G. The organic dye is dissolved in solvents like: water,benzene,alcohol,ethanol .

6. Active medium(cont’) Organic dye + Water,Benzene,Ethanol e.t.c = Active Medium Concentration of dye solution is kept around 10e-2 to 10e-4 Mole.

7. Pumping Source/Excitation Lasers Energy to excite the dye is supplied by a strong light source that may be a flash lamp or other as listed below. Flash lamps and several types of lasers can be used to optically pump dye lasers. A partial list of excitation lasers include: Copper vapor lasers Diode lasers Excimer lasers Nd:YAG lasers (mainly second and third harmonics) Nitrogen lasers Ruby lasers Argon ion lasers in the CW regime Krypton ion lasers in the CW regime

8. Pumping Source/Excitation Lasers Here the pumping source is a mono-chromatic laser( excimer laser). Q-what is a pumping source? To achieve Stimulated emission,we need more atoms in higher energy state(E2).This phenomenon is achieved by bombardment of photons.So pumping source is actually a source of Photons.

9. Resonator Resonators are Mirrors. The most useful feature of dye Lasers is their tunability,means the lasing wavelength can be varied over a wide range. Due to this reason ,dye lasers are also called Tunable Lasers. One of the technique to obtain tuning is to replace one of the mirrors with Diffraction grating,by rotating the grating the wavelength of dye laser can be altered.Thus tunability is obtained.

10. Construction

11. Basics Absorption Emission (Intensity) Absorption Emission (m)

12. Emission Emission can be of two types: Fluorescence Phosphorescence Fluorescence: It means when a photon hits dye,it immediately (zero time delay) emits light. Phosphorescence: In phosphorescence there will be some time delay. Both these Phenomenon occurs due to nature of different organic dyes.

13. Energy Level Diagram

14. Electromagnetic Spectrum Diagram

15. Advantages Low cost Tuning possible with multiple means No degradation of the optical properties of the organic dye. More robust(professional) and compact systems.

16. Disadvantages limited lifetime. limited output power

17. Applications Dye lasers are used to spectroscopy, holography and in Medical applications. A recent application of dye laser was in isotope separation.