Time-Domain Terahertz - Toptica

Standard PackageHigh PowerExtensionPhase Mod.ExtensionBasic & CompleteSpectroscopy ExtensionAC Bias~DFB laser #1TXAmplifiersample positionDFB laser #2RXLock-inDetectionIncludesIncludesIncludesIncludesIncludes· 2 DFB diode lasers,· Semiconductor· Twin fiber· 2 GaAs· All components850 nm or 1550 nmor fiber amplifierstretcher,or InGaAsof Basic· Complete driver electronics· Fiber coupling at inputSM/PM fibersphotomixersSpectroscopy· FPGA-based frequency controland output· HV driver· PhotocurrentExtension· Fiber-optic beam combination· SM/PM fiber splitter,amplifier· 2 parabolic50:50 %· Softwaremirrors andinterfacemirror mounts· Precisionalignmentstagesfor photomixersDigital lock-in amplifierThe terahertz signal – the photocurrent in the receiver – resides in the pico- tonanoampère range. Recovering this faint signal requires lock-in detection: Theterahertz beam is periodically chopped and the readout circuit “looks” at the signalmodulation at the chopping frequency. The faster the chopping, the more efficientthe detection becomes. An elegant way to achieve kHz-rate chopping is to modulatethe bias voltage of the terahertz transmitter.In all of TOPTICA’s cw terahertz systems, the TeraControl unit acts as a digital lock-inamplifier for the terahertz signal. The FPGA-based module feeds an AC bias to thetransmitter and de-modulates the receiver photocurrent. In addition, the TeraControltunes the terahertz frequency by precisely adjusting the temperatures of both DFBlasers.TeraControl – digital lock-in modulewith USB interface.