ISOMET RFA0110-1 Series User manual

Oct 15
RF Amplifier
Including: Basic Modulator Alignment
D1345-aQ110-4
Instruction Manual
RFA0110-1-x Series
Models -
RFA0110-1 : 90-140MHz, amplifier module, 12W output
Options -x:
ISOMET CORP, 5263 Port Royal Rd, Springfield, VA 22151, USA.
Tel: [phone], Fax: [phone], e-mail: [e-mail]
www.ISOMET.com
ISOMET (UK) Ltd, 18 Llantarnam Park, Cwmbran, Torfaen, NP44 3AX, UK.
Tel: [phone], Fax: [phone], e-mail: [e-mail]
ISOMET

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1. GENERAL
The RFA0110-1 Power Amplifier, figure 1, contains a fixed gain broadband RF amplifier specifically
designed to operate with Isomet acousto-optic devices such as the D1345-aQ110. The driver
requires low level RF signal from a suitable frequency source such as the Isomet iMS4-L frequency
synthesizer. Figure 2 is a functional block diagram of the driver.
The rise and fall response time for the amplifier is approx’25nsec.
This amplifier is designed to operate at full rated power into a 50

load with 100% duty cycle.
Trace 1 = RF output
Trace 2 = Sync signal
Water cooling is optional.
The heatsink temperature must not exceed 70

C.
SERIOUS DAMAGE TO THE AMPLIFIER MAY RESULT IF THE TEMPERATURE EXCEEDS 70

C.
SERIOUS DAMAGE TO THE AMPLIFIER MAY ALSO RESULT IF THE RF OUTPUT CONNECTOR
IS OPERATED OPEN-CIRCUITED OR SHORT-CIRCUITED.
A low impedance d-c power source is required. The operating voltage is +24V or +28Vdc at a current
drain of approximately 3A (4A maximum). The external power source should be regulated to

2%
and the power supply ripple voltage should be less than 200mV for best results.
Higher RF output power is achieved at 28Vdc.

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2.1 LED INDICATOR
The front panel tri-colour LED indicates the operating state.
LED Stack
RED
The top LED will illuminate RED when 24Vdc supply is applied.
Normal condition is ON
YELLOW
The middle LED will illuminate YELLOW, when the RF Gate input is valid.
(Default condition = valid, unless a connection is made to pin7 of the D-type)
Normal condition is ON, but may be OFF if the above conditions are not met
GREEN
The lower LED will illuminate GREEN when the following signals are all true:
1) RF DC power is applied and
2) Gate signal is valid and
3) Amplifier and AO thermal interlocks are valid *.
Normal condition is ON
* Thermal Interlocks
The AOM and Driver are fitted with thermostatic switches which will switch open circuit if a
predetermined temperature is exceeded. These thermal interlocks will reset once the AO device and /
or RF driver are cooled below this temperature.
- The driver thermal switch over-temperature threshold is 50deg C
- The AOD thermal switch over-temperature threshold is 36deg C
The hysteresis of the thermal switches is 7-10deg C.
Once in a fault state the coolant temperature will need to be reduced to reset the thermal
switches.

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3.0 INSTALLATION AND ADJUSTMENT
Please refer to the Synthesizer manual for frequency, phase and amplitude control of the
input signals.
3.1 For water cooled AO devices;
Connect cooling water at a flow of more than 1 litres/minute at < 20 deg.C to both the RF
amplifier and AO device. Due to the RF power dissipated in the AO modulator, it is paramount
that the device is operated only when water cooling is circulating. For optimum AO
performance, ensure the flow rate is greater than 1 litre /minute at < 20 deg.C.
3.2 For conduction cooled AO devices;
Ensure the AOM and RF driver are mounted to a good heat conduction surface
3.3 With no d-c power applied, connect the + 24V (or +28V) DC in to the screw terminal.
DO NOT APPLY POWER.
3.4 Connect the RF output BNC jacks to the acousto-optic deflector (or a 50

RF load, if to
measure the modulator RF output power).
Connection order depends onthe orientation as shown on page 12.
Relative phase delay depends on the input source.
3.3a Connect the RF input SMA jacks to the external frequency source outputs
(90 –130MHz, 1mW max, 50

, each input).
3.4 Connect the Interlock of the acousto-optic device to the mating connector of the RF driver
(Binder 3pin snap connector).
The interlock connection becomes open circuit disabling the RF output, if the temperature of
the modulator exceeds 36ºC or the internal driver temperature exceeds 50ºC. The LED
indicator illuminates when the Interlocks are closed and the RF is enabled (see Section 2).
3.5 Adjustment of the RF output power is best done with amplifier connected to the acousto-optic
modulator.

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3.6 The optimum RF power level required for the modulator to produce maximum first
order intensity will be different at various laser wavelengths. Applying RF power in
excess of this optimum level will cause a decrease in first order intensity (a false
indication of insufficient RF power ) and makes accurate Bragg alignment difficult. It
is therefore recommended that initial alignment be performed at a low RF power level.
3.7 Set the input power level to give approximately 4W output.
3.8 Apply DC power to the amplifier.
3.9 Apply a constant RF input to the input SMA connector of the RFA0110-1 (ref: 3.7)
Input the laser beam toward the centre of either aperture of the AO device. Ensure the polarization is
vertical with respect to the base and the beam height does not exceed the active aperture height of
the AOM/AOD.
Start with the laser beam normal to the input optical face of the AOD and very slowly rotate the AOD
(see page 12 for configurations.)
3.10 Observe the diffracted first-order output from the acousto-optic modulator and the undeflected
zeroth order beam. Adjust the Bragg angle (rotate the modulator) to maximise first order
beam intensity.
3.11 After Bragg angle has been optimized, slowly increase the RF input power until maximum first
order intensity is obtained. This should occur at < 10W peak for the D1345-aQ110-4 at
374nm.

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3.12 To equalise deflection efficiency at the extremes of the scan, alternate between the minimum
and maximum desired frequencies and adjust Bragg angle to give the same efficiency for
both. (Note: the photo detector or light power meter will require repositioning for the two
angles.) .
Typical swept frequency response at 374nm
First order sweep
RF power on 25% duty cycle

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4. MAINTENANCE
4.1 Cleaning
It is of utmost importance that the optical apertures of the deflector optical head be kept clean and
free of contamination. When the device is not in use, the apertures may be protected by a covering of
masking tape. When in use, frequently clean the apertures with a pressurized jet of filtered, dry air.
It will probably be necessary in time to wipe the coated window surfaces of atmospherically deposited
films. Although the coatings are hard and durable, care must be taken to avoid gouging of the surface
and leaving residues. It is suggested that the coatings be wiped with a soft ball of brushed (short
fibres removed) cotton, slightly moistened with clean alcohol. Before the alcohol has had time to dry
on the surface, wipe again with dry cotton in a smooth, continuous stroke. Examine the surface for
residue and, if necessary, repeat the cleaning.
4.2 Troubleshooting
No troubleshooting procedures are proposed other than a check of alignment and operating
procedure. If difficulties arise, take note of the symptoms and contact the manufacturer.
4.3 Repairs
In the event of deflector malfunction, discontinue operation and immediately contact the manufacturer
or his representative. Due to the high sensitive of tuning procedures and the possible damage which
may result, no user repairs are allowed. Evidence that an attempt has been made to open the optical
head will void the manufacturer's warranty.

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RFA 0110-2 Standard Version
Connection Summary
1.0 ‘D’ Type Control Connection
Signal Type Pin out connection
Digital Gate Input Signal pin 7
Return pin 2
CMOS high (12V logic) or NC = ON
CMOS low (0.0v<V<1v) = OFF
2.0 Coaxial SMA (2)
Low level RF Input
Frequency range 90 –130MHz Typical
80 –140MHz Maximum
Power level 0dBm (1mW) Typical
3dBm (2mW) Maximum
3.0 Interlock connection
3 1
2
3 1
2
RFDriver INTPlug
(OK = connected
contacts 1-2)
AOMThermal Interlock Plug
(OK = connected contacts
1-2)
The interlock signal must be connected. Contacts closed for normal operation.
4.0 Mounting Holes
4 x M5

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RF DRIVER
MODEL :
S/N :
ISOMETISOMET
200
120
190
158520
CTRL
24V
0V
RF outputs
(BNC)
IN1
G1/8" Threaded
Optional Water Fittings
8mm OD pipe
DC Supply Input
Screw Terminals
RF input
(SMA)
RF1
PWR
73
20
Figure 1: Driver Installation

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+Vdc
+Vdc
+
RF
Output
-GATE
(D-type)
SMA
RF
Input
PA
Transistor
Figure 2: Driver Block Diagram

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1st
0th
Input
Orientation options
Input
Input
Input
1st
1st
1st
0th
0th
0th
J1
First Order
Diffracted Beam
Zero Order
Input Laser Beam
D1345-aQ110 Separation
Angle
Separation Angle at 355nm
110MHz = 6.85 mrad
Bragg Angle at 355nm
3.43 mrad (Nominal)
Bragg
Angle
Scan Angle
Scan Angle at 355nm
105MHz -125MHz = 1.25 mrad
100MHz -140MHz = 2.5 mrad
RFA0110-1
RF1
INT
RF inputs:
(0dBm max)
Beam Dump
"Knife edge"
reflector
IN1 IN1
IN2
9w-D
Figure 4: Typical Connection Configuration
Diagram shows typical beam alignment..
Laser can be input either side of AOM.
See connection options below.

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Schematic of a single electrode acousto optic deflector
and tunable driver
RF
1st Order Scan
0th Order
Input Laser Beam
Intensity Modulation
Tuning Voltage



SEP
SCAN
BRAGG
AO Deflector
Deflector Driver
The input bragg angle, relative to a normal to the optical surface and in the plane of deflection is :
BRAGG = fc
2.v
The separation angle between the zeroth order and mid scan point of the first order is :  
SEP = fc
v
The first order scan angle is :
SCAN= f
v
where: = wavelength
  fc = centre frequency = 110MHz
v = acoustic velocity of interaction material = 5.7mm/usec (a-Quartz)
d = 1/e2beam diameter
Figure 5. Deflection System