Solvent Effect on Absolute Fluorescence Quantum Yield of Rhodamine 6G Determined Using Transient Thermal Lens Technique

Dual beam thermal lens tecbnique is successfully employed for the determination of absolute Fluorescence quantum yield of rhodamine 6G lnser dye in different solvents. A 532 nm radiation from a Q-switched Nd:YAG laser was used for the excitation purpose. The fluorescence quantum yield values are found to be strongly influenced by environmental effects. It has been observed that fluorescence yield is greater for rhodamine 6G in ethylene glycol system than in water or in methanol. Our results also indicate that parameters like concentration of the dye solution, aggregate formation and excited state absorption affect the absolute values of fluorescence yield significantly.

Effect of silver nano particles on the fluorescence quantum yield of Rhodamine 6G determined using dual beam thermal lens method

Nano structured noble metals have very important applications in diverse fields as photovoltaics, catalysis, electronic and magnetic devices, etc. Here, we report the application of dual beam thermal lens technique for the determination of the effect of silver sol on the absolute fluorescence quantum yield (FQY) of the laser dye rhodamine 6G. A 532 nm radiation from a diode pumped solid state laser was used as the excitation source. It has been observed that the presence of silver sol decreases the fluorescence quantum efficiency. This is expected to have a very important consequence in enhancing Raman scattering which is an important spectrochemical tool that provides information on molecular structures. We have also observed that the presence of silver sol can enhance the thermal lens signal which makes the detection of the signal easier at any concentration.

Thermal lens technique to evaluate the fluorescence quantum yield of a schiff base

The fluorescence spectrum of the schiff base obtained from salicylaldehyde and 2-aminophenol is studied using an argon-ion laser as the excitation source and its fluorescence quantum yield (Qf) is determined using a thermal lens method. This is a nondestructive technique that gives the absolute value of Qf without the need for a fluorescence standard. The quantum-yield values are calculated for various concentrations of the solution in chloroform and also for various excitation wavelengths. The value of Qf is relatively high, and is concentration dependent. The maximum value of Qf obtained is nearly 0.78. The high value of the fluorescence quantum yield will render the schiff base useful as a fluorescent marker for biological applications. Photostability and gain studies will assess its suitability as a laser dye.

Two and Three Photon Absorption in Rhodamine 6G Methanol Solutions Using Pulsed Thermal Lens Technique

Dual beam transient thermal lens studies were carried out in rhodamine 6G methanol solutions using 532 nm pulses from a frequency doubled Nd:YAG laser. Analysis of thermal lens signal shows the existence of different nonlinear processes like two photon absorption and three photon absorption phenomena along with one photon absorption. Concentration of the dye in the solution has been found to influence the occurrence of the different processes in a significant way.

Laser Induced Thermal Lens Effect in Rhodamine B — Signature of Resonant Two Photon Absorption

Measurement of thermal lensing signal as a function of laser power made in Rhodamine B solutions in methanol give clear evidence of two photon absorption process within certain concentration ranges when 488 nm Ar+ laser beam is used as the pump source. Only one photon process is found to occur when 514 nm and 476 nm beams are used as the pump.

Investigations of Optical Interaction Processes in Certain Photonic Materials Using Z-scan and Thermal Lens Techniques

International School of Photonics, Cochin University of Science and Technology

Laser induced thermal lens and near infrared absorption studies of ch overtones in some organic compounds

Vibrational overtone spectroscopy of X-H (X=C,N,O) containing molecules is an area of recent interest. The spectroscopic studies of higher vibrational levels yield valuable informations, regarding,the molecular structure, intra- and inter-molecular interactions, radiationless transitions, intra-molecular vibrational relaxations, multiphoton excitations and chemical reactivities, which cannot be z obtained by other spectroscopic methods. This thesis presents the results of experimental investigations on the overtone spectra of some organic compounds in the liquid phase for the characterization of CH bonds. The spectra in the fifth overtone region (1fiV=6) are recorded using a dual beam thermal lens setup and the lower overtones (.AV=2-5) are recorded spectrophotometrically.The thesis is presented in six chapters.