Quantum Instruments Cascade Laser Starter Kit QCL pulse switching measuring unit, Generalities

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vP high

Starter Kit Instruction Manual

Description

21

4.6QCL pulse switching measuring unit

4.6.1Generalities

The measuring circuit contained in the LDD100 provides information about various laser pulse pa- rameters (peak voltages, supply voltages, duty cy- cle, frequency). They are only estimated values, since exact measurement of short and strong pulses with diodes and averaging circuitry is diﬃcult.

Keep in mind that you should always measure the voltages on the LLH100 if you need accurate time and voltage data (see ﬁnal paragraph). How- ever, these data are useful for monitoring and surveil- lance purposes, and to give a rough estimation of the current parameters.

4.6.2Measured voltages

•UHV: 1/2 of the average voltage, respective to VHT (user supplied high voltage)

•ULH: 1/2 of the average laser anode voltage, respective to VHT

•ULL: duty cycle dependent peak laser cathode voltage, respective to VHT

•UD: duty cycle dependent peak transistor drain voltage, respective to VHT

•UPI: 1/2 average internally reshaped drive volt- age, respective to ground

•UPT: 1/2 average of a 37ns ﬁxed length pulse, respective to ground

4.6.3Timing data

Pulse frequency calculation

UPT can be used to calculate the pulse frequency as follows:

f= f 2U P T −νP low

0 νP high −νP low

Where f0 is a frequency constant, vP low and are the TTL pulser voltage limits.

Actual values: f0 = 371 ns , vP low =0.01V, vP high =5V

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Contents Quantum Cascade Laser Starter Kit Instructions Manual Web versionContents Maintenance Overview InstallationTroubleshooting UseAppendix Limited waranty IdentiﬁcationDocument ManufacturerGeneralities GeneralChapter overview ComplianceProduct GlossaryPersons PersonnelTypographic conventions Commands styleProcedure style Description styleSee page x-y Troubleshooting style ProblemProcedure eﬀects style Possible causePage Non-compliance with the safety regulations Safety InstructionsImportance of safety instructions IntroductionEnvironmental conditions General safety instructionsCompliance and informa- tion Description System CompositionDescription DFB and FP Quantum Cascade LasersIf no conﬁguration is speciﬁed, the DN pad is used Geometry of QC lasersSpeciﬁcations Electrical model characteristics Electrical modelLaboratory Laser HousingLLH100 LLH100 external view descriptionLaboratory Laser Housing internal view LLH100 internal viewSpeciﬁcations of the Peltier connector Thermo-Electric Cooler TEC and PT100 connectionsSpeciﬁcations of the measurement connector Measurement connectionQCL pulser switching unitLDD100 QCL pulser switching unit front and rear viewMeasured voltages QCL pulse switching measuring unitGeneralities Timing dataLaser peak current Duty cycle calculationAverage dissipation Laser peak voltageAccuracy considerations Trigger and logic output signals Ω TTL driver circuit QCL pulser timing unit TPG128QCL temperature controllerTCU151 Peltier and PT100 connectionsGeneral InstallationChapter overview Packing list Standard itemsProcedure Setting the appropriate AC voltage on TCU151110-120V, 60Hz USA 220-240V, 50Hz Europe Installing the starter Kit Before beginningConnecting Starter Kit Use QCL pulse timing unit com- mand descriptionTCU151 command description TCU151 temperature controler front panelOverview Laser utilisationProceedings Starting the TPG128 Procedure Interlock utilisation Interlock utilisationDC power supply is not ﬂoating TroubleshootingPower supply reaches max cur- rent for a very low voltage PrincipleQCL laser is not used with the LLH and is grounded Laser draws current but gives no lightLaser does not draw current There is no contact with the laserHow to remove the covers of TCU151 and TPG128 MaintenanceOverview Replacement procedures Quantum Cascade Laser replace MentFacet on the case, it is extremely fragile + LLH100 connectionQCL UP and DN position Exchange Exchanging the laserIf the ambient atmosphere is humid this is HumidityBefore beggining interlock set Ting TCU151 temperature con Troller interlock settingProcedure interlock setting Needed material1 TPG128 calibration Calibaration proceduresProcedure calibration GeneralitiesTPG128 main board TPG128 main board 2 TCU151 temperature controller calibration Procedure +5V/-5V power supply checkSensing level and range adjustement = 1.22 toTemperature Reference oﬀset adjustment Oscillator check Current/Voltage ratio adjustmentSetting LCD screen should display 1.00 a7V = 70 C If needed, adjust it with the trimmer P92 Starting the power section of the instru Ment→ Value displayed ≤ 1A Current adjustment→ Value displayed should tend to the deﬁned value Threshold on Miscellaneous functions testing Temperature Limit testing→ The temperature displayed 2 should be 035 C → The red LED 1 should turn oﬀDirect absorption Application notesDetection techniques Frequency modulation technique TildasPhotoacoustic detection Photoacoustic techniqueBias Circut Bias-T AppendixGeneral Utilisation What has to be kept in mind before use? Current and voltage ranges of the Bias-T cir- cuit Avoid reverse polarity on the inputUnpacking NS laser from its transportation box Unpacking instructions for NS submounts