A. Pulse Power Supply for High Power Laser

1. High Peak current pulsed power supply for solid state lasers

2. High voltage and high speed trigger circuits

3. 150 kJ single-shot pulsed power supplies for Nd:Glass Disk Laser Amplifiers

4. Simmer mode pulsed power supply for small-size krypton lamps

5. Development of High Power Pulse Power Supply for Copper Vapour Laser and its Application

   a) Development of copper vapour laser and its variants

   b) Development of pulsed power supply for copper vapour lasers

   c) Application of copper vapor laser (Micromachining setup)

High peak current pulsed power Supply for solid state laser

Specifications of 2-beam high power laser power supply:

S. No.	Parameters	values
1.	Input	400 V, 3-phase, 50Hz
2.	Charging voltage (Max.)	5kV
3.	Total installed capacity	1.5MJ
4.	Peak discharge current per flash	6kA
5.	Charging time (Max.)	40s
6.	Pulse duration	500us
7.	Peak power per flash	2.5kJ at 500us
8.	Repetition rate	Single shot
9.	Cooling mechanism	Air cooled
10.	Operation mode	Unipolar/bipolar

Specifications of power supplies for faraday isolator:

S. No.	Parameters	values
1.	Charging voltage (Max.)	5kV
2.	Installed capacity	16kJ
3.	Pulse width	3ms
4.	Coil inductance	2.5mH
5.	Peak magnetic field	1.5T

2. High voltage and high speed trigger circuits:


High Voltage & High Speed Trigger Circuits

High power and high energy lasers, their subsystems, laser plasma interaction experimental setups and Electro-optical devices need high voltage and fast rise time trigger signals. The division has expertise in development of trigger switches based on a variety of switches such as Ignitron, Thyratron, Avalanche transistors and SCRs for these applications.

The pulsed power supplies consists of multiple 10 kV rated capacitor banks to store up to 150 kJ electrical energy for driving 400 mm arclength xenon flashlamps in high power pulsed mode. These flashlamps function as pump sources in Nd: glass disk based solid state laser amplifiers. Preionization scheme has been adopted to increase pumping efficiency and flashlamp life. It involves delivering a low energy prepulse prior to main discharge pulse. Prepulse is maintained within 5 to 10% of main pulse with delay of 200 μs to 300 μs between the two. A 10 kV constant current source based on resonant converter topology has been developed to charge capacitor banks. For discharge of stored energy, HV flashlamp trigger circuits based on series triggering method and high peak pulsed current (~100 kA) rated ignitron switches are used. Figure 1 shows the developed power supplies and figure 2 shows a typical flashlamp pulse.

Small-size krypton lamps are mostly used as pump sources in Nd:YLF or Nd: YAG based laser oscillators in high power laser chains. Simmer mode power supply have been developed to drive krypton lamps (up to 2 in series) of arc length up to 100 mm at pulse repetition rate of ≤ 10 Hz.

For better pulse-to-pulse stability and enhancement of flashlamp life, simmer mode has been incorporated wherein flashlamps are kept in conducting state by a dc current of more than 100 mA during successive pulses by a separate HV dc power supply. The flashlamps have been operated at per pulse energy of up to 240 joules at capacitor bank voltage of 2 kV. Figure 3 shows the developed power supply and figure 4 shows a typical flashlamp current pulse.

Copper Vapour Laser Electronics Laboratory works on design, development and maintenance of copper laser systems. Many models of elemental Copper Vapour Laser, Copper Bromide Lasers and Copper HyBrID lasers giving average laser power from 4 W to 100 W from single unit are developed. The lasers operate with pulse repetition rate of 5 to 20 kHz and typical pulse width (FWHM) of 40 nS. The laser wavelength of these units are 510 nm (green) and 578 nm (yellow). These lasers are used in various applications like second harmonic generation for Fibre Bragg Grating (FBG) inscription, pumping dye lasers, spectroscopy, micromachining etc.

Elemental copper vapour lasers are typically operated at 6 kHz with electrical to optical efficiency of about 1% whereas Copper Bromide and Copper HyBrID lasers operate at high repetition rate of 18 KHz with higher efficiency of 2 %. The warm time of Copper Bromide and Copper HyBrID laser is 15 min whereas elemental copper vapour laser is 45 min. The development of laser system requires multidisciplinary expertise in the field of high vacuum, high temperature, thermal insulation, high voltage, precise gas flow, precise electronic control and instrumentation and EMC/EMI.

• Timer Control Unit: A timer control unit is developed to generate control signals for three IGBTs. The dead time between the control signals and timing of pulses can be varied in the range of 5 µs to 75 µs for each channel. The unit is a plug in module of size 3U, 12T and can be operated in internal and external mode (glass fibre) of operation.
  
  
• Gas and Vacuum Control Unit
  
  
• Pressure and Temperature Monitoring Card
  
  
• IGBT driver Card : A dual channel IGBT driver card using driver IC M57962L is developed to drive IGBTs rated for 1200 V, 150 A to 400 A. The card requires +15 VDC for its operation.
  
  
• Precise delay generator Unit, 0 to 255 ns with resolution of 1 ns
  
  
• Programmable Logic Controller Unit for monitoring and control of Laser and DC power supply

Specifications of IGBT based solid state pulse power supply for 40 W Copper Vapour Laser Input: Three phase, 415 VAC mains, 50 Hz Output peak voltage: 25 kV Peak current: 900 A Pulse repetition rate: 6.5 kHzp Rise time: 80 ns Average output power: 5 kW Pulse generator topology: IGBT based capacitor to capacitor charge transfer circuit with MPC Cabinet size: 19” / 36U rack, 800mm depth Cooling: Water cooled