Con­fo­cal THz Laser Micro­scope

Beschreibung

The tera­hertz (THz) ran­ge refers to fre­quen­ci­es bet­ween 0.1 and 10 THz and repres­ents the spec­tral gap bet­ween the micro­wa­ve and infra­red regi­on. Over the past few years, the­re has been a signi­fi­cant inte­rest in employ­ing THz tech­no­lo­gy in spec­tro­scopy, ima­ging, and recent­ly in short-ran­ge indoor com­mu­ni­ca­ti­on sys­tems. THz radia­ti­on can be gene­ra­ted by dif­fe­rent sche­mes. Among them are the Far-Infra­red (FIR) lasers which are pre­fer­red for their wide ran­ge of pos­si­ble out­put fre­quen­ci­es and their high con­ti­nuous-wave out­put power. In this the­sis a FIR laser is pre­sen­ted and its working mecha­nism is descri­bed in detail. THz waves are able to pene­tra­te most non-metal­lic objects and pose no health risk for human bein­gs as they do not have any ioni­zing pro­per­ties unli­ke for examp­le X‑rays. This makes THz radia­ti­on ide­al for ima­ging app­li­ca­ti­ons. An effec­ti­ve tech­ni­que for ima­ging of small objects in thick sam­ples is the so-cal­led con­fo­cal micro­scopy. In this work we trans­fer the princip­le of opti­cal con­fo­cal micro­scopy to the THz ran­ge using a FIR laser source. Detec­tion of THz radia­ti­on repres­ents one of the major hurd­les which impe­de the com­mer­cial use of a prac­ti­cal and cost-effec­ti­ve THz sys­tem. Here some exis­ting and new FIR laser detec­tors are pre­sen­ted and their working mecha­nism are dis­cus­sed.