Quantum Instruments Cascade Laser Starter Kit manual

Starter Kit Instruction Manual

Maintenance

9.1.3Photoacoustic detection

In the photoacoustic detection, the optical beam is periodically modulated in amplitude before illumi- nating the cell containing the absorbing chemical. The expansion generated by the periodic heating of the chemical creates an acoustic wave which is detected by a microphone.

The two very important advantages of photoa- coustic detection are:

•a signal is detected only in the presence of absorption from the molecule;

•no mid-IR detectors are needed.

For these reasons, photoacoustic detection has the potential of being cheap and very sensitive. How- ever, ultimate sensitivity is usually limited by the optical power of the source.

a.c. modulation of	Detection of the
the laser amplitude	acoustic wave at w
w
QC Laser	Chemical Cell
	Microphone

Fig.53: Photoacoustic technique

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Quantum Instruments Cascade Laser Starter Kit manual Photoacoustic detection, Photoacoustic technique

Contents

Instructions Manual Web version Quantum Cascade Laser Starter Kit Contents Use InstallationTroubleshooting Maintenance Overview Appendix Manufacturer IdentiﬁcationDocument Limited waranty Compliance GeneralChapter overview Generalities Personnel GlossaryPersons Product Description style Commands styleProcedure style Typographic conventions Possible cause ProblemProcedure eﬀects style See page x-y Troubleshooting stylePage Introduction Safety InstructionsImportance of safety instructions Non-compliance with the safety regulations Environmental conditions General safety instructionsCompliance and informa- tion System Composition Description Geometry of QC lasers DFB and FP Quantum Cascade LasersIf no conﬁguration is speciﬁed, the DN pad is used Description Speciﬁcations Electrical model Electrical model characteristics LLH100 external view description Laboratory Laser HousingLLH100 LLH100 internal view Laboratory Laser Housing internal view Thermo-Electric Cooler TEC and PT100 connections Speciﬁcations of the Peltier connector Measurement connection Speciﬁcations of the measurement connector QCL pulser switching unit front and rear view QCL pulser switching unitLDD100 Timing data QCL pulse switching measuring unitGeneralities Measured voltages Duty cycle calculation Laser peak current Average dissipation Laser peak voltageAccuracy considerations QCL pulser timing unit TPG128 Trigger and logic output signals Ω TTL driver circuit Peltier and PT100 connections QCL temperature controllerTCU151 Standard items InstallationChapter overview Packing list General Procedure Setting the appropriate AC voltage on TCU151110-120V, 60Hz USA 220-240V, 50Hz Europe Before beginning Installing the starter Kit Connecting Starter Kit QCL pulse timing unit com- mand description Use TCU151 temperature controler front panel TCU151 command description Overview Laser utilisationProceedings Starting the TPG128 Interlock utilisation Procedure Interlock utilisation Principle TroubleshootingPower supply reaches max cur- rent for a very low voltage DC power supply is not ﬂoating There is no contact with the laser Laser draws current but gives no lightLaser does not draw current QCL laser is not used with the LLH and is grounded How to remove the covers of TCU151 and TPG128 MaintenanceOverview Quantum Cascade Laser replace Ment Replacement procedures + LLH100 connection Facet on the case, it is extremely fragile Exchanging the laser QCL UP and DN position Exchange Humidity If the ambient atmosphere is humid this is Needed material TCU151 temperature con Troller interlock settingProcedure interlock setting Before beggining interlock set Ting Generalities Calibaration proceduresProcedure calibration 1 TPG128 calibration TPG128 main board TPG128 main board Procedure +5V/-5V power supply check 2 TCU151 temperature controller calibration = 1.22 to Sensing level and range adjustement Temperature Reference oﬀset adjustment LCD screen should display 1.00 a Current/Voltage ratio adjustmentSetting Oscillator check Starting the power section of the instru Ment 7V = 70 C If needed, adjust it with the trimmer P92 → Value displayed ≤ 1A Current adjustment→ Value displayed should tend to the deﬁned value → The red LED 1 should turn oﬀ Miscellaneous functions testing Temperature Limit testing→ The temperature displayed 2 should be 035 C Threshold on Frequency modulation technique Tildas Application notesDetection techniques Direct absorption Photoacoustic technique Photoacoustic detection Bias Circut Bias-T AppendixGeneral Utilisation What has to be kept in mind before use? Avoid reverse polarity on the input Current and voltage ranges of the Bias-T cir- cuit Unpacking instructions for NS submounts Unpacking NS laser from its transportation box

Quantum Instruments Cascade Laser Starter Kit Photoacoustic detection, Photoacoustic technique

Models: Cascade Laser Starter Kit

9.1.3Photoacoustic detection

Fig.53: Photoacoustic technique