The Q or Quality factor of a laser cavity describes the ability of the cavity to store light energy in the form of standing waves. The Q factor is the ratio of energy contained in the cavity divided by the energy lost during each round trip in the cavity:
This means that a cavity with high losses dissipates a lot of energy per cycle hence it has a low Q value. A high Q cavity means the energy loss per cycle is small in the given cavity. By inserting a device in the cavity which is capable of controlling the loss of a cavity, we are effectively controlling the Q of the cavity. This device acts as an optical shutter or switch inside the cavity, which, when closed, absorbs or scatters the light, resulting in a lossy, low Q cavity. When the shutter is open, the cavity becomes low loss, high Q. This switch is called a Q-SWITCH. Acousto-optic Q-Switches A Q-switch is a special modulator which introduces high repetition rate losses inside a laser cavity (typ 1 to 100 KHz). They are designed for minimum insertion loss and to be able to withstand very high laser powers. In normal use an RF signal is applied to diffract a portion of the laser cavity flux out of the cavity. This increases the cavity losses and prevents from oscillation. When the RF signal is switched off, the cavity losses decrease rapidly and an intense laser pulse evolves.
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It is essential in Q-switching to correlate the timing sequence of the optical pumping mechanism with the Q-switching. This means the following : Assume that at the time when the laser pumping is turned on, the Q of the cavity is low. The high loss prevents laser action occurring so the energy from the pumping source is deposited in the upper laser level of the medium At the instant, when the population inversion is at its highest level, the switch is suddenly open to reduce the cavity loss Because of the very large built up population difference, laser oscillations will quickly start and the stored energy is emitted in a single giant pulse.
The lasing stops because the pulse quickly depopulates the upper lasing level to such an extent that the gain is reduced to below threshold. This operation is periodically repeated in order to obtain the operating regime.
 
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10 to 20 Watts RF drivers
REF
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QMODP0xx
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QMODP1xx
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QMODP2xx - Ultra Compact
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Carrier Frequency
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27.12, 40.68, 64, 80 MHz
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27.12, 40.68, 64, 80 MHz
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27.12, 40.68, 64, 80 MHz
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Power Supply
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24 VDC (on request 15 VDC)
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24 VDC
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24 VDC
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Rise/Fall Time
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< 50 ns
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< 50 ns
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< 50 ns
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Digital Input
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TTL / 1 Kohms
(on request TTL Reversed)
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TTL Reversed / 1 Kohms
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TTL / 1 Kohms
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Analog Power input
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Analog 0-5 V/ 10 Kohms
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Analog 0-5 V/ 10 Kohms
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Through external screw potentiometer
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Output RF Power
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10, 15 or 20 Watts
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20 Watts
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20 Watts (on request 2 to 20 W)
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Output Power measurement
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No
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Yes
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Yes
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Returned Power measurement
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No
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Yes
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Yes
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Thermal security / Alarm for QST
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No
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Yes
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Yes
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Themal security / Alarm for driver
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No
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Yes
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Yes
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Size
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129 x 61 x 54 mm3
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143 x 110 x 20 mm3
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70 x 60 x 24 mm3
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Heat Exchange
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Includes heatsink + Fan
Conduction through baseplate
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Conduction through baseplate
Must be attached to an external heatsink
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Conduction through baseplate
Must be attached to an external heatsink
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Max Case temperature
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70 °C
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70 °C
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70 °C
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30 to 70 Watts RF drivers
REF
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QMODP1xx
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Carrier Frequency
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27.12, 40.68 MHz
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Power Supply
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24 VDC
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Rise/Fall Time
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< 50 ns
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Digital Input
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TTL Reversed / 1 Kohms (on request TTL)
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Analog Power input
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Analog 0-5 V/ 10 Kohms
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Output RF Power
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30, 50, 70 Watts
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Output Power measurement
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Yes
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Returned Power measurement
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Yes
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Thermal security / Alarm for QST
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Yes
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Themal security / Alarm for driver
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Yes
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Size
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143 x 110 x 20 mm3
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Heat Exchange
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Conduction through baseplate
Must be attached to an external heatsink
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Max Case temperature
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70 °C
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100 to 120 Watts RF drivers
REF
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QMODP3xxx
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Carrier Frequency
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27.12, 40.68 MHz
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Power Supply
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24 VDC
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Rise/Fall Time
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< 100 ns
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Digital Input
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TTL Reversed / 1 Kohms (on request TTL)
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Analog Power input
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Analog 0-5 V/ 10 Kohms
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Output RF Power
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100-120 Watts
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Output Power measurement
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Yes
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Returned Power measurement
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Yes
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Thermal security / Alarm for QST
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Yes
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Themal security / Alarm for driver
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Yes
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Size
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183 x 140 x 26 mm3
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| Heat Exchange |
Conduction through baseplate
Must be attached to an external heatsink
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| Max Case temperature |
70 °C
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Dual output 2x30 or 2x60 Watts RF drivers, for double Q-switches operation
Under certain circumstances, it is necessary to drive simultaneously 2 crossed Q-switches. AA offers its new range of drivers which will allow user to drive in synchronism both Q-switches, with only one drive signal, thanks to its balanced dual outputs.
REF
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QMODP4xxx
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Carrier Frequency
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27.12, 40.68 MHz
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Power Supply
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24 VDC
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Rise/Fall Time
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< 80 ns
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Digital Input
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TTL Reversed / 1 Kohm (on request TTL)
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Analog Power input
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Analog 0-5 V/ 10 Kohms
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Output RF Power
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2x30 or 2x60 Watts
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Output Power measurement
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Yes
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Returned Power measurement
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Yes
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Thermal security / Alarm for QST
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Yes
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Themal security / Alarm for driver
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Yes
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| Size |
183 x 140 x 25 mm3
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| Heat Exchange |
Conduction through baseplate
Must be attached to an external heatsink
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| Max Case temperature |
70 °C
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