Jogy George
Articles written in Pramana – Journal of Physics
Volume 52 Issue 6 June 1999 pp 623-629 Research Articles
Rakesh Kapoor P K Mukhopadhyay Jogy George S K Sharma
A simple derivation, which relates the thermal lens focal length in solid state lasers to pump power and a method for direct estimation of thermal lens focal length, is reported. This method is applicable to any type of stable resonator. The method is used for the measurement of the thermal lens focal length with an accuracy of 8% in an axially pumped microchip laser. The variation of focal length with pump power is also measured.
Volume 53 Issue 2 August 1999 pp 307-319
Rakesh Kapoor PK Mukhopadhyay Jogy George SK Sharma
An alternative approach is suggested to determine the spot-size of a multi-mode laser beam. It has been shown by simulations that the suggested approach can give the beam quality factor and characteristic radius with less than 5% error. Unlike the power content method, the proposed method is applicable to the beams even with diameter one tenth of the CCD size. The new approach has been applied to a multi-mode diode laser output and it is shown that the
Volume 56 Issue 1 January 2001 pp 77-85 Research Articles
PK Mukhopadhyay Jogy George SK Sharma Rakesh Kapoor TPS Nathan
In this paper an alternative approach for measurement of
Volume 58 Issue 1 January 2002 pp 59-66 Research Articles
Operational characteristics of dual gain single cavity Nd:YVO4 laser
Pranab K Mukhopadhyay Jogy George S K Sharma P K Gupta T P S Nathan
Operational characteristics of a dual gain single cavity Nd:YVO4 laser have been investigated. With semiconductor diode laser pump power of 2 W, 800 mW output was obtained with a slope efficiency of 49%. Further, by changing the relative orientation of the two crystals the polarization characteristics of the output could be varied. In particular by keeping the two Nd:YVO4 crystals with their
Volume 58 Issue 4 April 2002 pp 657-668 Research Articles
Effect of absorbed pump power on the quality of output beam from monolithic microchip lasers
Pranab K Mukhopadhyay K Ranganathan Jogy George SK Sharma TPS Nathan
The dependence of the beam propagation factor (
Volume 59 Issue 1 July 2002 pp 75-89 Research Articles
Pranab K Mukhopadhyay K Ranganathan Jogy George SK Sharma TPS Nathan
The effect of Nd3+ concentration on the CW and Q-switched laser performances at 1064 nm from Nd: YVO4 has been studied under diode laser pumping in identical laser configuration. The Nd3+ concentrations used were 1, 2 and 3 at.% in YVO4 crystals. Under the CW operations we have compared the thermal lensing effect, slope efficiencies and also the beam quality at the fourth-order degeneracy configuration. Q-switching was done with the help of an acousto-optic modulator and we have compared the pulses obtained from Nd: YVO4 laser with different doping concentration. It was found that the 1 at.%-doped crystal is the best, offering highest optical-to-optical conversion efficiency (55%), lowest fractional heat load (24%), highest pulse energy (80
Volume 68 Issue 4 April 2007 pp 571-580 Research Articles
An alternative method to specify the degree of resonator stability
Jogy George K Ranganathan T P S Nathan
We present an alternative method to specify the stability of real stable resonators. We introduce the degree of optical stability or the 𝑆 parameter, which specify the stability of resonators in a numerical scale ranging from 0 to 100%. The value of zero corresponds to marginally stable resonator and $S < 0$ corresponds to unstable resonator. Also, three definitions of the S parameter are provided: in terms of $A&D$, $B&Z_{\text{R0}}$ and $g_{1}g_{2}$. It may be noticed from the present formalism that the maximum degree of stability with $S = 1$ automatically corresponds to $g_{1}g_{2} = 1/2$. We also describe the method to measure the 𝑆 parameter from the output beam characteristics and 𝐵 parameter. A possible correlation between the 𝑆 parameter and the misalignment tolerance is also discussed.
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