Lithuanian Journal of Physics article / Lietuvos fizikos žurnalo straipsnis

STUDY OF THE LOW-COST HIPS AND PARAFFIN-BASED TERAHERTZ OPTICAL COMPONENTS
Kasparas Stanaitis^a,b, Karolis Redeckas^a,b, Augustė Bielevičiūtė^a,b, Matas Bernatonis^a,b, Domas Jokubauskis^a, Vladislovas Čižas^a, and Linas Minkevičius^a,b
^aDepartment of Optoelectronics, Center for Physical Sciences and Technology, Saulėtekio 3, 10257 Vilnius, Lithuania
^bFaculty of Physics, Vilnius University, Saulėtekio 9, 10222 Vilnius, Lithuania
Email: kasparas.stanaitis@ftmc.lt

Received 26 October 2023; accepted 27 October 2023

The ever-increasing popularity of the terahertz (THz) frequency range reveals the increasingly obvious applicability limiting factor – the price of the final setup. This study is intended to contribute to the solution by evaluating the THz frequency range suitability of the optical components, fabricated using two easily accessible materials – high impact polystyrene (HIPS) and paraffin. The primary analysis using time-domain spectroscopy (TDS) revealed promising results, as both materials had sufficient refractive indexes of n ≈ 1.55 and a high transmittance. That allowed one to assume the feasibility of creating a low-cost THz frequency range lens. Lenses of focal lengths of f = 20, 30, 40 mm were fabricated using extrusion 3D printing and paraffin moulding. The produced lenses showcased the satisfactory beam focusing ability, comparable to that of already existing much less cost-efficient solutions. The THz imaging using the fabricated lenses has successfully been realized, proving the applicational possibilities of the imaging system with the proposed low-cost components employed.
Keywords: terahertz frequency range, beam shaping, paraffin lenses, THz imaging, 3D printed lenses

ŽEMOS KAINOS TERAHERCINĖS OPTIKOS KOMPONENTAI IŠ POLISTIRENO IR PARAFINO
Kasparas Stanaitis^a,b, Karolis Redeckas^a,b, Augustė Bielevičiūtė^a,b, Matas Bernatonis^a,b, Domas Jokubauskis^a, Vladislovas Čižas^a, Linas Minkevičius^a,b

^aFizinių ir technologijos mokslų centro Optoelektronikos skyrius, Vilnius, Lietuva
^bVilniaus universiteto Fizikos fakultetas, Vilnius, Lietuva

Terahercinė (THz) spinduliuotė yra perspektyvi ir nuolat besiplečianti optoelektronikos sritis. Šis elektromagnetinių bangų ruožas naudojamas daugybėje įvairių taikymo sričių, įskaitant objektų vaizdų registravimą ir analizę. Plačiai pritaikyti šį dažnių ruožą trukdo aukšta įrangos kaina bei sudėtinga komponentų gamyba. Būtent šią problemą siekiama išspręsti, gaminant optinius komponentus iš pigių ir lengvai prieinamų medžiagų – parafino ir smūgiams atsparaus polistireno (HIPS). Šių medžiagų analizė laikinės skyros spektroskopijos metodu (angl. time-domain spectroscopy), atskleidė, kad abi šios medžiagos yra tinkamos sub-THz spinduliuotei dėl sąlyginai aukšto lūžio rodiklio n ≈ 1,55 ir gero pralaidumo tame ruože. Šie parametrai atvėrė galimybę pagaminti lęšius teraherciniam bangų ruožui – naudojantis 3D spausdinimo technologija, pagaminta po tris parafino bei polistireno lęšius, kurių židinio nuotoliai f = 20, 30, 40 mm. Pagaminti optiniai komponentai pasižymi gera spinduliuotės fokusavimo kokybe, palyginti su daug brangesniais ir sudėtingiau gaminamais lęšiais. Vaizdinimo sistema charakterizuota panaudojus MTF (modulation transfer function) vaizdinant modifikuotą USAF1951 taikinį. Komponentai sėkmingai pritaikyti terahercinėje vaizdinimo sistemoje, vaizdinant kredito kortelę popieriniame voke. Parodyta, kad norint sėkmingai panaudoti THz spinduliuotės ruožą, brangūs ir sunkiai prieinami komponentai yra nebūtini.

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