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3.5 Locking to an atomic transition:

AC

29

4. Adjust the

INPUT OFFSET

such that saturated absorption trace

is near zero.

5. Switch the modulation on with

OFF/MOD

.

6. Find an appropriate spectral peak and observe the dispersive

error signal with

CHAN B

set to

ERROR

.

7. Optimise the error signal (usually for maximum slope) by ad-

justing the front panel

PHASE

. The error signal slope should

normally be positive (depending on

DIP

switches

10, 11

) at the

desired frequency.

8. Adjust the

GAIN

such that the error peaks are roughly 250 mV

peak-to-peak.

9. Adjust front-panel

LOCK OFFSET

such that the error signal is

crossing zero at the desired frequency.

10. Set

SLOW

and

FAST

gains to minimum (fully anti-clockwise).

11. Switch

SCAN

/

LOCK

to

LOCK

.

12. Switch

OFF

/

LOCK

to

LOCK

.

PD

250kHz

M

Lock-in

Servo

Vapour cell + coil

λ/4

f 

~ 150mm

f 

~ −25mm

Optical

isolator

λ/2

PBS

PBS

ECDL

Figure 3.6:

Schematic setup for a more compact and more easily aligned

saturated absorption arrangement. PD is the

DLC

photodetector. PBS

polarising beamsplitter, M mirror,

λ/

4 and

λ/

2 retarders. Beam expanding

lenses increase the signal power while minimising saturation broadening.

Summary of Contents for DLC202

Page 1: ...External Cavity Diode Laser Controller Models DLC 202 DLC 252 DLC 502 Revision 6 00 ...

Page 2: ...idental or consequential damages in connections with or arising out of the performance or use of any of its products The foregoing limitation of liability shall be equally applicable to any service provided by MOGlabs Copyright Copyright c MOG Laboratories Pty Ltd MOGlabs 2010 No part of this publication may be reproduced stored in a retrieval system or transmitted in any form or by any means elec...

Page 3: ...o an atomic transition In addition to current and temperature con trollers we provide piezo drivers sweep ramp generator modulator for AC locking lock in amplifier feedback servo system laser head electronics protection board even a high speed low noise balanced photodetector We would like to thank the many people that have contributed their hard work ideas and inspiration especially Lincoln Turne...

Page 4: ...ii ...

Page 5: ...y be connected to this socket CAUTION Please ensure that the unit is configured for the correct voltage for your AC mains supply before connecting The supply must include a good ground connection WARNING The internal circuit boards and many of the mounted compo nents are at high voltage with exposed conductors in partic ular the high voltage piezo driver circuitry The unit should not be operated w...

Page 6: ...nt supplied through the RF connector on the laser headboard is not limited Cable continuity If the laser is disconnected the system will switch to standby and disable all laser and piezo power supplies If the laser diode TEC or temperature sensor fail and become open circuit they will be disabled accordingly Short circuit If the laser diode TEC or temperature sensor fail and become short circuit o...

Page 7: ...s when laser is switched on Mains filter Protection against mains transients Key operated The laser cannot be powered unless the key operated STANDBY switch is in the RUN position to enable protection against unauthorised or accidental use Interlocks Both the main unit and the laser head board have interlocks to allow disabling of the laser via a remote switch or a switch on the laser cover ...

Page 8: ...s not fall under the scope defined in RoHS Directive 2002 95 EC and is not subject to compliance in accordance with DIRECTIVE 2002 95 EC Out of Scope Electron ics related Intended application is for Monitoring and Control or Medical Instrumentation MOG Laboratories Pty Ltd makes no claims or inferences of the compliance status of its products if used other than for their intended purpose vi ...

Page 9: ...ntrols 7 2 1 Front panel controls 7 2 2 Front panel display monitor 10 2 3 Rear panel controls and connections 12 2 4 Internal switches and adjustments 14 3 Operation 21 3 1 Simplest configuration 21 3 2 Laser frequency control 22 3 3 External scan control 24 3 4 Locking to an atomic transition DC 24 3 5 Locking to an atomic transition AC 27 3 6 Locking using an external signal 30 3 7 External con...

Page 10: ... impedance 48 C 3 Impedance matching 49 C 4 Tuning 50 C 5 Shielding 51 D External modulators and injection current modulation 53 D 1 Coupling circuit 53 D 2 Injection current modulation 54 E Photodetector 57 E 1 Photodiodes 58 F Laser head board 59 F 1 Headboard connectors 59 F 2 Grating pivot point compensation 60 F 3 RF coupling 61 G Connector pinouts 63 G 1 Photodetector 63 G 2 Laser 63 G 3 Int...

Page 11: ...bs DLC is read ily connected to a laser diode temperature sensor and thermo electric cooler via the provided laser head board In the simplest applica tion the DLC will con trol the diode current and temperature Thus the DLC must be connected to the diode a thermoelectric Peltier cooler TEC and a temperature sensor All connections between the MOGlabs DLC and the laser head are via a single cable An...

Page 12: ...cur rent or with high voltage 120 V outputs for piezo electric actuators to control the cavity length of an ECDL The actuators should be con nected to the laser head board via the provided MOLEX connectors One or two piezo elements can be controlled Typically only a single stack actuator such as the Tokin AE0203D04 available from Thorlabs www thorlabs com will be required The single stack actuator...

Page 13: ...ing is to the side of an absorption peak in a vapour cell see for example Demtro der 5 for more information on spectroscopy The passive configura tion of 1 2 is extended with the MOGlabs DLC photodetector see appendix E and an atomic vapour absorption cell Alternately a Fabry Perot optical cavity or other reference could be used The schematic shows a saturated absorption spectroscopy arrange ment ...

Page 14: ...of inherently lower detected noise and thus the potential for improved laser frequency stability The setup is similar to that for DC locking but modulation of the laser fre quency or the reference frequency is required The MOGlabs DLC provides an internal 250 kHz oscillator which can directly dither the diode current or drive an external modulator In particular it is designed to drive a Zeeman shi...

Page 15: ...apour cell coil AOM λ 4 λ 4 Figure 1 5 Schematic setup for AC locking to an atomic transition PD is the DLC photodetector BS beamsplitter M mirror λ 4 a quarter wave retarder the diode current see 2 4 Feedback can again be via one or both piezo actuators the diode current or all three ...

Page 16: ...6 Chapter 1 Introduction ...

Page 17: ... the high voltage piezo power and the main on board low voltage power In RUN mode the DLC activates all circuits including the laser cur rent driver and piezo drivers The diode current is disabled and the STACK is on but not scanning until the laser enable switch is ON On first power up the STANDBY indicator will be red this is normal and indicates there has been a power failure since last switche...

Page 18: ...cription in section A 2 PHASE When AC locking the controller demodulates the error signal from the detected light intensity PHASE adjusts the relative phase be tween the internal reference modulator and the detected signal from 0 to 360 When DC locking the sign of the error signal can be flipped by rotating the PHASE control GAIN Overall error signal gain 0 to 40 dB SLOW Gain for feedback to the s...

Page 19: ...switching from scan to lock the controller will first reset the scanning actuator usually STACK to the offset voltage at the trigger point and then lock to the nearest frequency at which the error signal is zero Sign of fast current feedback The sign of the slow feedback can be changed with the PHASE control for both AC and DC locking OFF LOCK Enable fast current feedback The laser can be locked w...

Page 20: ... current Current to thermoelectric Peltier cooler A TEC voltage Voltage on thermoelectric Peltier cooler V Frequency Frequency actuator offset usually slow piezo normalised to a range of 1 CHAN A Several important signals can also be monitored externally with an oscilloscope via the rear connectors CHANNEL A CHANNEL B and TRIG The outputs to these can be selected with the CHAN A and CHAN B selecto...

Page 21: ...2 2 Front panel display monitor 11 CHAN B Input Photodetector 30 mV µW Error Feedback error Current Diode current to monitor bias 10 V A Mod Modulator output current 1 V A Temp Temperature error 10 V C ...

Page 22: ...er a monitoring oscilloscope It is provided to minimise ground loop noise problems Fan The fan speed is temperature controlled Interlock The DLC will not power on the laser unless the pins on this connector are shorted A standard 2 1 mm DC plug is provided LASER Connection to laser head This connector provides diode current two piezo drives temperature sense and TEC current A DVI D Dual cable is p...

Page 23: ...tch 6 ON the sensitivity is 2 5 mA per volt with the fast gain knob set to the middle of its range SWEEP PZT MOD Input for externally generated frequency control STACK DIP switch 9 and or DIP switch 13 or for piezo DISC modulation DIP switch 14 External sweep signal should be 0 to 2 5 V and must cross 1 25 V to generate necessary triggering internally Impedance 5 kΩ Sensi tivity 48 V per volt 120 ...

Page 24: ... STACK fixed STACK ON 3 Current dither OFF Current dither ON 4 Current bias OFF Current bias ON 5 Internal error External error 6 External current mod OFF External current mod ON 7 AC lock DC lock 8 Single photodiode Dual photodiode 9 Internal sweep External sweep 10 STACK feedback STACK feedback 11 STACK sweep STACK sweep 12 AC current feedback DC current feedback 13 STACK internal STACK external...

Page 25: ...ause frequency modulation of the laser frequency In conjunction with a frequency dependent absorption on the photode tector signal for example with an atomic vapour cell or etalon see section 3 5 The modulation depth is adjusted via internal trimpot RT6 and the modulation can be switched on and off via the front panel toggle switch OFF MOD DIP 4 Enables injection current bias sometimes called feed...

Page 26: ...ference between the two photodiode signals is controlled in the photodetector itself DIP 9 13 14 15 These switches determine the function of the EXT SWEEP input for example to provide an external frequency ramp or to use an exter nal locking circuit see section 3 6 or to allow measurement of the actuator response functions DIP 9 With DIP 9 ON the laser frequency sweep will be driven from an extern...

Page 27: ... a Fabry Perot adjusted such that the laser is on the side of a fringe or on the side of a saturated absorption transmission peak in a vapour cell e g fig 1 4 DIP 15 If DIP 15 is on the normal internally generated feedback error signal is replaced with the EXT SWEEP input DIP 12 16 Switches 12 16 allow operation of DFB DBR lasers without external cavity feedback and thus with only current as an ac...

Page 28: ...GH to SLOW lock regardless of the state of the front panel switch LOW to sweep if the front panel switch is up FAST HIGH to FAST lock HOLD HIGH to enable sample and hold With HOLD active the feedback to the slow piezo will be fixed by a sample and hold circuit The diode current can then be modulated via the rear panel CURR MOD input with DIP switch 6 ON to jump the laser frequency quickly without ...

Page 29: ...rent can be modulated directly The modulation depth is then controlled by the rear panel Imod trimpot The limit to the current modulation is factory set via RT6 RT12 A phase lead circuit is included on the current feedback channel to boost the output at higher frequencies tens of kHz RT12 con trols the phase lead and can be adjusted for different diodes see appendix 4 RT13 Offset adjustment for ac...

Page 30: ...20 Chapter 2 Connections and controls ...

Page 31: ...the diode TEC and sensor to the laser head board fig 1 1 using the provided MOLEX 2 and 3 pin connectors Please note the polarities 2 Adjust the temperature setpoint first select Temp set on the display selector then adjust Tset via the front panel trimpot 3 Ensure the power is on and the STANDBY RUN switch is on STANDBY In this mode most circuits will be switched off in cluding much of the main i...

Page 32: ... the limit is being displayed rather than the actual current 9 Switch the laser on The indicator on the laser head board should illuminate and the front panel indicator above the switch should turn green Note that the SCAN LOCK and fast channel OFF LOCK switches must be set to SCAN and OFF respectively Other protection features will prevent current to the diode including main cable disconnect and ...

Page 33: ...ee scan range The two actuators can be driven equally so that only the cavity length will vary with out rotation or with a large ratio so that the grating rotates while translating See appendix F for more information 0V 0V 120V time TRIG STACK 5V FREQUENCY SPAN SPAN Figure 3 1 Stack output voltage and trigger signal when scanning In normal SCAN mode a sawtooth ramp is supplied to the the stack at ...

Page 34: ...d return of the STACK sweep drive can excite mechanical oscillations in the laser Slower sweeps are recommended usually 20 Hz works well but if ringing is observed at the start of the sweep reduce fsweep 3 3 External scan control An external source can be used to control the laser frequency while in SCAN mode 1 Connect the external frequency control ramp or DC signal to the rear panel SWEEP extern...

Page 35: ... lower trace the AC modulation error signal see 3 5 an atomic vapour absorption cell A Fabry Perot optical cavity or other frequency reference could also be used The photodetector can be used in single channel mode default or with balanced differential inputs for example to subtract a Doppler background from a saturated absorption spectrum Sample oscilloscope traces obtained in DC locking side of ...

Page 36: ...ignals upper traces 4 Connect the DLC photodetector module 5 Using an optical beamsplitter a stray reflection or by other means deflect a fraction of the laser output through the vapour cell The MOGlabs DLC is designed to operate best with about 250 µW incident on each of the Si PIN photodiodes Lensed and filtered photodiodes are standard to minimise the influ ence of background light but best res...

Page 37: ...om in on the desired lock point The controller will automatically lock to the zero crossing closest to the trigger point i e to the centre of the oscilloscope trace When the laser is locked step 10 above the photodetector INPUT signal should be fixed at the value corresponding to the lock fre quency in this case zero since for DC locking the controller locks to the zero crossing 3 5 Locking to an ...

Page 38: ...odule and optimise the photosig nal on CHANNEL A The MOGlabs DLC is designed to operate best with about 250 µW incident on the Si PIN photodiode Lensed and filtered photodiodes are standard to remove most background light and when AC locking at 250 kHz modula tion frequency any remaining photocurrent from background lighting should not be a problem BS PD 250kHz M M BS Lock in ECDL BS Servo Vapour ...

Page 39: ...djust the GAIN such that the error peaks are roughly 250 mV peak to peak 9 Adjust front panel LOCK OFFSET such that the error signal is crossing zero at the desired frequency 10 Set SLOW and FAST gains to minimum fully anti clockwise 11 Switch SCAN LOCK to LOCK 12 Switch OFF LOCK to LOCK PD 250kHz M Lock in Servo Vapour cell coil λ 4 f 150mm f 25mm Optical isolator λ 2 PBS PBS ECDL Figure 3 6 Sche...

Page 40: ... will automatically lock to the zero crossing of the error signal in this case the peak of a spectral feature closest to the trigger point at the centre of the oscilloscope trace When the laser is locked step 11 above the photodetector INPUT signal should be fixed at the value corresponding to the lock fre quency In contrast to the DC locking case this should be the INPUT signal at the peak of the...

Page 41: ...t locking signals can be separated A fast lock signal can be input on EXT ERROR and enabled via DIP 6 and a slow signal can at the same time be input on EXT SWEEP and enabled via DIP 15 3 7 External control of lock frequency setpoint It is often useful to have external control of the lock frequency set point for example to suddenly change the detuning of a laser The rear panel ERROR external input...

Page 42: ...32 Chapter 3 Operation ...

Page 43: ...ature and reduce the effective linewidth as close as possible to the S T limit Achieving the best frequency locking stability requires careful op timisation of the signal to noise ratio SNR of the frequency dis crimination signal obtained from the saturated absorption or other reference Then the phase and gain settings must be optimised preferably by measuring the feedback error signal spectrum 4 ...

Page 44: ...olarisation The frequency discriminator ERROR signal is sensitive to the pump and probe polarisations Good polarisers and careful alignment can be very helpful Coil design See appendix C Shielding The Zeeman coil produces substantial magnetic fields oscillating at 250 kHz These fields can readily induce prob lematic potentials and currents in the laser head and or main circuit board In particular ...

Page 45: ...trum analyser can be used to provide better guidance A generic computer sound card with spectrum analysis software gives reasonable results up to 20 kHz A good sound card 24 bit 200 kHz e g Lynx L22 or E Mu 1212m provides noise analysis up to 100 kHz with 140 dB dynamic range surpassing most standalone audio spectrum analysers at very low cost Connect the spectrum analyser to the CHANNEL B output ...

Page 46: ...on the diode optical feedback the frequency discriminator noise floor and other details Typically we find that the laser diode itself has a 90 phase lag at 15 to 100 kHz Some compensation for that phase lag is provided by a phase lead compensator see RT12 page 19 Ideally the SLOW and FAST gains should be adjusted to minimise the integrated noise the area under the error spectrum The data in fig 4 ...

Page 47: ... 50 Ω 160 kHz 2 5 GHz See spectrum below BIAS 25 mA over full sweep Temperature controller TEC current max 2 5 A TEC voltage max 9 V TEC power max 22 W Stability 5 mK C Sensor NTC 10 kΩ AD590 AD592 Range 0 30 standard extended range optional Display resolution 0 01 Note The TEC current is controlled with a linear regulator The regulator will overheat if the current load is high and the TEC voltage...

Page 48: ...labs for further information Note The maximum piezo drive current is 10 mA which limits the scan rates for piezos with high capacitance For exmaple for a 250 nF piezo the rate should not be greater than 25 Hz Photodetector Photodiodes Si PIN IR filtered 740 nm 1100 nm 1 1 mm2 sensor 10 field of view See appendix E for spectral response Options unfiltered 400 nm 1100 nm 20 70 Coupling AC and DC sin...

Page 49: ...ER 20 dB FAST MASTER 20 dB Bandwidth gains at midpoint SLOW 0 dB at 700 Hz FAST 0 dB at 80 kHz Protection and status External interlock 2 1 mm DC power plug provided Laser head enclosure interlock 2 pin MOLEX connector provided Key switch interlock STANDBY RUN Delayed soft start 1 s delay 1 5 s ramp Open circuit detect Laser cable TEC temperature sensor Diode current limit Rear panel trimpot Imax ...

Page 50: ...ult Either LOCK switch ON in terlock open head cable dis connected temperature con troller fault detected ORANGE Ready GREEN Diode running Mechanical power Display 4 5 digit LED standard colour red Fan 12 V DC ball bearing Temperature controlled IEC input 110 to 130 V 60Hz or 220 to 260 V 50Hz Fuse 5x20mm anti surge slo blo ceramic 250V 2 5A IEC output Common ground with power input Intended for o...

Page 51: ...ignal is output via the rear panel TRIG connection for synchronising to an oscilloscope or external experiment The span may be limited by the minimum and maximum voltage that can be applied to the actuator 0 and 120 V 150 V optional That is the ramp may saturate as shown in fig A 2 The period remains fixed and the trigger remains at the centre of the period but the laser frequency will not scan fo...

Page 52: ...ions 0V 0V 120V time TRIG STACK 5V FREQUENCY SPAN Figure A 2 STACK output voltage and trigger pulse when FREQUENCY is set near the midpoint upper or moved closer to 0 V lower where the output voltage exceeds the maximum range ...

Page 53: ...RUN Possible faults AC mains off Interlock s disconnected TEC open or short circuit TEC polarity reversed Cable disconnected Temperature sensor disconnected Active temperature sensor connected to thermistor pins Thermistor connected to active sensor pins Temperature out of range 5 C or 35 C External sweep selected DIP switch 9 but no external sweep supplied RED AC mains power failure temperature c...

Page 54: ...cted TEC disabled temperature out of range Any one of 5 10 12 V internal supplies below nominal by more than 1 V External sweep selected DIP switch 9 but no external sweep supplied ORANGE Standby above conditions satisfied diode ready to start GREEN Diode fully operational piezos active If the indicator remains ORANGE after switching the diode ON check the possible faults listed above in particula...

Page 55: ... one of the slow actuators STACK DISC STACK feedback has wrong polarity See DIP switch 10 Lock signal zero crossing too far from trigger point Gain too high Try smaller and smaller gain but be careful to ensure that the lock error signal is crossing zero Loop response too fast for actuator The controller is normally shipped with slow channel response gain of 1 0dB around 700 Hz Please contact the ...

Page 56: ...t very slightly Lock signal zero crossing too far from trigger point Gain too high Try smaller and smaller gain but be careful to ensure that the lock error signal is crossing zero B 3 4 FAST locks only briefly The FAST channel is normally AC coupled see DIP switch 12 with a time constant of 0 1 s Thus with FAST feedback only the laser will drift off resonance Normally the SLOW channel is used to ...

Page 57: ...ow cost using a solenoid coil wrapped around an atomic vapour cell as shown below Figure C 1 Vapour cell Zeeman coil and primary excitation coil mounted on PCB available from MOGlabs C 1 Field requirements Ideally the Zeeman dither coil should produce a frequency shift of about half the peak width typically a few MHz Atomic stretched state transitions will be Zeeman shifted by µB eh 2me 1 4 MHz Ga...

Page 58: ...and l is the coil length In practice the inductance will be less e g see Wheeler 9 LWheeler N2r2 228r 254l mH C 2 4 where N is the total number of turns r is the coil radius in metres and l is the length in metres l 0 8r We have found that for dimensions typical of coils wound around vapour cells these two formulae agree within a factor of two Note that the inductance increases with n2 whereas the...

Page 59: ...lew rate of 6 V µs This can be impedance matched to a high current coil using a trans former or quite effectively by directly winding a primary on the main Zeeman coil as shown in the photo above For the main Zeeman coil 0 4 mm to 0 6 mm diameter wire wound around the vapour cell about 120 to 200 turns works well The coil is balanced for the standard modulation frequency of ω 250 kHz using a capac...

Page 60: ...dequate voltage rating C 4 Tuning To maximise the current in the secondary the capacitor should be chosen to tune the circuit to the DLC modulation frequency A spec trum analyser with tracking generator is particularly helpful con nect the coil to the TG output and to the SA input and sweep through the resonance see figure Alternately drive the coil with a function generator and measure the magnet...

Page 61: ...kHz C 5 Shielding Large magnetic fields oscillating at 250 kHz can readily cause prob lematic electromagnetic interference EMI Induction in the laser head or the cable to the laser head can easily produce substantial diode current modulation The coil and vapour cell should be lo cated far from the laser and from the controller or shielded with soft iron or a high permeability alloy such as mu meta...

Page 62: ...52 Appendix C Modulation coils ...

Page 63: ...iode injection current DIP switch 3 or drive an external modulator such as an electro optic modulator EOM or acousto optic modulator AOM D 1 Coupling circuit The DLC provides a current controlled modulation output with 1 Ω sense resistor It can be directly connected to a 50 Ω load producing a voltage of 5 V with Iset adjusted to 100 mA Impedance matching and a DC level shift may be needed to drive...

Page 64: ...ion e g 10 MHz via the SMA RF input on the laser head board Very narrow linewidths can be achieved with suitably high bandwidth frequency discrimination for example by phase locking two lasers The diagram below shows an arrangement to lock two lasers to an EIT electromagnetically induced transparency reso nance which obtained a beatnote linewidth below 1 kHz 10 Photodiode Phase shifter Lowpass 2 5...

Page 65: ...l is returned to the external error input on the probe laser MOGlabs DLC which locked the laser with bandwidth up to about 40 kHz The error signal was also coupled through a single stage passive phase lead high pass filter and then combined with the 10 MHz modulation using a passive bias tee and injected into the SMA modulation input to provide feedback bandwidth of about 600 kHz Att 25 dB RBW 300...

Page 66: ...56 Appendix D External modulators and injection current modulation ...

Page 67: ...the rear socket and cable provided A number of M4 and 8 32 threaded holes allow mounting in different configurations to minimise the footprint on an optical bench see figure E 2 Figure E 1 MOGlabs DLC balanced differential photodetector 1 2 Figure E 2 M4 mounting holes are marked with a circular ring others are 8 32 Single channel photodiode 1 differential signal 1 2 57 ...

Page 68: ...ance angles are also available Photodiode Specifications Parameter Standard Options Spectral range 10 of max 750 1100 nm 400 1100 nm Peak sensitivity 900 nm 850 nm Half angle 10 20 75 Sensitive area 1 1 mm2 Max incident power 500 µW Apparent sensitivity CHAN A 30 mV µW λ nm 0 Relative detection efficiency 400 600 800 1000 1200 20 40 60 80 100 0 400 600 800 1000 1200 20 40 60 80 100 λ nm Relative d...

Page 69: ... tee The laser head board can be mounted to the supplied laser head panel Figure F 1 MOGlabs DLC laser head board showing headers for con nection of laser diode piezo actuators temperature sensor TEC and head enclosure interlock F 1 Headboard connectors P1 Microwave RF modulation input SMA P3 Diode SMA high bandwidth HD1 Diode MOLEX low bandwidth HD2 Active temperature sensor AD590 or AD592 HD3 Pe...

Page 70: ...ment RT1 of the voltage ratio between the two By driving two stacks the effective grating pivot point can be optimised to extend the mode hop free scan range The two actuators can be driven equally so that only the cavity length will vary without rotation or with a large ratio so that the grating rotates while translating LENS OUTPUT BEAM LASER DIODE GRATING PIVOT STACK PRIMARY STACK SECONDARY G R...

Page 71: ...bias tee such as the Mini Circuits ZFBT 4R2GW FT between the head board and the diode The input sensitivity depends on the diode impedance typically about 50 Ω Thus a 0 dBm signal corresponds to about 0 2 V and a current of around 4 mA at the diode That is the current sensitiv ity is approximately 20 mA V WARNING The RF input is a direct connection to the laser diode Excessive power can destroy th...

Page 72: ... 20 Pair 5 21 P6 Shield 22 Pair 6 23 Pair 6 24 Mount Hole D1 1 2 3 HD1 R3 10k0 R4 43R DNI D2 Active sensor Active sensor Sig Gnd P1 SMA 5P Laser Interlock Lid posiiton interlock Voltage Free contact that closes when box in posiiton 1 2 HD4 Flying leads R2 4k99 C4 250V 10nF Sig Gnd P3 SMA 5P h t d i w d n a b h g i h F R e d o i d o t n o i t c e n n o c L1 100uH 1 2 7 8 NC U1A 3 4 5 6 NC U1B R1 39...

Page 73: ...onsumer digital display devices It should only be connected to the corresponding MOGlabs laser head board It supplies the high voltage signals to drive the laser piezo electric actuators In principle the piezo drivers will be disabled if the cable is disconnected but nevertheless considerable care should be taken to ensure that non MOGlabs devices are not connected via this connector The MOGlabs c...

Page 74: ...ay 5V 23 NTC 8 16 Interlock 5V 24 NTC 1 8 17 24 Figure G 2 LASER connector on rear panel G 3 Interlock The rear panel interlock socket is a standard 2 1 mm cylindrical DC power jack The outer conductor is supplied with 5 V via a 5 k re sistor The inner pin is connected to ground via a 10 k resistor The laser should be enabled by shorting the two contacts LASER ENABLE ø2 1mm 5V 5k ø6 5mm Figure G 3...

Page 75: ...he lock point as described in section 2 4 The signals are standard TTL compatible 2 4 V HIGH and 0 8 V LOW The inputs are ORed with the front toggle switches such that the signal is activated if either the digital input is active i e HIGH or the toggle switch is on down Pin Signal Pin 1 Laser ON OFF 2 GND 3 Lock Sweep 4 GND 5 Fast Lock 6 GND 7 Hold 8 GND 9 5 V 10 GND ...

Page 76: ...66 Appendix G Connector pinouts ...

Page 77: ...5 R171 U4 1 D9 R310 C1 31 R341 C147 C150 R257 D8 TR11 C108 C110 L1 5 C122 C1 14 U7 7 R298 R280 U7 1 C1 23 H3 U8 5 H4 R334 C142 C145 U9 2 H5 R314 U7 9 D1 0 L1 8 R3 21 R3 20 C140 U8 0 U8 1 C133 R330 R3 22 R3 28 R3 29 R335 U8 7 N2 R342 R343 C146 C148 R3 47 R3 48 U9 5 R3 51 U9 1 TR 13 R3 49 D1 TR 14 U9 3 R354 R353 R358 R359 R361 R360 U9 6 U9 7 U6 5 R2 64 U6 6 R267 U6 7 R266 C1 15 C117 R271 C4 31 U7 3 ...

Page 78: ...68 Appendix H PCB layout ...

Page 79: ... with external cavity diode lasers Appl Opt 48 36 6961 2009 i 5 W Demtro der Laser Spectroscopy Basic Concepts and Instru mentation Springer Berlin 2e edition 1996 3 33 6 R W P Drever J L Hall F V Kowalski J Hough G M Ford A J Munley and H Ward Laser phase and frequency stabilization using an optical resonator Appl Phys B 31 97 105 1983 30 54 55 7 L D Turner K P Weber C J Hawthorn and R E Scholten...

Page 80: ...n Laser frequency offset locking using electromagnetically in duced transparency Appl Phys Lett 90 171120 2007 54 11 G C Bjorklund Frequency modulation spectroscopy a new method for measuring weak absorptions and dispersions Opt Lett 5 15 1980 54 55 70 ...

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Page 82: ...ries Pty Ltd 420 Victoria St Brunswick VIC 3056 Australia Tel 61 3 9940 1427 Fax 61 3 9381 0700 info moglabs com c 2010 Product specifications and descriptions in this doc ument are subject to change without notice ...

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