Laser processing for precise fabrication of the THz optics

Voisiat, Bogdan; Indrišiūnas, Simonas; Šniaukas, Ramūnas; Minkevičius, Linas; Kašalynas, Irmantas; Račiukaitis, Gediminas

doi:10.1117/12.2253634

Cited by 10 publications

(7 citation statements)

References 10 publications

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“…They allow obtaining elements with large numerical aperture values (NA) and assure a compact optical setup configuration in comparison to refractive or reflective counterparts. Here, direct laser writing [ 68 ] (related to ablating the unwanted parts of the substrate layer) ensures proper manufacturing resolution. However, such a technique can be also used to manufacture phase structures with different number of phase steps [ 3 , 69 , 70 ] or even kinoform structures [ 71 ].…”

Section: Efficient Focusing Of Thz Radiationmentioning

confidence: 99%

The Magic of Optics—An Overview of Recent Advanced Terahertz Diffractive Optical Elements

Siemion

2020

Sensors

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Diffractive optical elements are well known for being not only flat but also lightweight, and are characterised by low attenuation. In different spectral ranges, they provide better efficiency than commonly used refractive lenses. An overview of the recently invented terahertz optical structures based on diffraction design is presented. The basic concepts of structure design together with various functioning of such elements are described. The methods for structure optimization are analysed and the new approach of using neural network is shown. The paper illustrates the variety of structures created by diffractive design and highlights optimization methods. Each structure has a particular complex transmittance that corresponds to the designed phase map. This precise control over the incident radiation phase changes is limited to the design wavelength. However, there are many ways to overcome this inconvenience allowing for broadband functioning.

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Section: Efficient Focusing Of Thz Radiationmentioning

confidence: 99%

The Magic of Optics—An Overview of Recent Advanced Terahertz Diffractive Optical Elements

Siemion

2020

Sensors

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“…However, a few of them were processed in an argon (Ar) atmosphere at a pressure of 1 or 2 atm. The samples were fabricated from a 500 ± 25 μm thick, both-sides polished, (100) crystal orientation highresistivity float zone silicon wafer that was similar to the ones used elsewhere [9], [12].…”

Section: Samples and Experimental Setupmentioning

confidence: 99%

“…The advantages of diffractive optics have been experimentally confirmed by demonstrating almost diffraction-limited imaging results [10], [11]. Silicon MPFLs have been fabricated using photo-lithography and the reactive ion etching technique [7] Manuscript received June 25, 2019; revised August 24, 2019 or using the maskless direct laser ablation (DLA) technology [12]. Moreover, the maskless laser patterning has been used to introduce additional functionalities in the MPFL, such as the phase-alteration structures working as both focusing and anti-reflective surfaces [13].…”

Section: Introductionmentioning

confidence: 99%

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Laser-Ablated Silicon in the Frequency Range From 0.1 to 4.7 THz

Indrišiūnas

Svirplys

Richter

et al. 2019

IEEE Trans. THz Sci. Technol.

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The optical performance of high-resistivity silicon with a laser-ablated surface was studied in the transmission mode in the frequency range of 0.1-4.7 THz. A reciprocal relationship between the transmission brightness and the surface roughness was observed at discrete THz frequencies. The measured dispersion was reproduced by the THz wave scattering theory using an effective refractive index model. No significant differences between the samples processed either with ps-or ns-duration laser pulses in ambient air or in argon enriched atmosphere were found in the THz regime. It was demonstrated that the majority of optical losses of the silicon with the laser modified surface were due to the scattering of THz waves and not due to the absorption in silicon-compounds formed during the laser ablation.

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“…Silicon wafer of 0.46 mm thickness was patterned using an industrial-scale-compatible laser direct writing (LDW) system based on a 1064 nm wavelength, 13 ps pulse duration, 1 MHz repetition rate, 60 µJ peak energy laser (Atlantic 60 from Ekspla Ltd.) [6]. The LDW technology enabled us to manufacture different complexity multilevel zone-phase elements in the same process with the opportunity to modify parameters in time.…”

Section: Samples and Fabricationmentioning

confidence: 99%

Compact diffractive optics for THz imaging

Minkevičius¹,

Indrišiūnas²,

Šniaukas³

et al. 2018

physics

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We present a compact diffractive silicon-based multilevel phase Fresnel lens (MPFL) with up to 50 mm in diameter and a numerical aperture up to 0.86 designed and fabricated for compact terahertz (THz) imaging systems. The laser direct writing technology based on a picosecond laser was used to fabricate diffractive optics on silicon with a different number of phase quantization levels P reaching an almost kinoform spherical surface needed for efficient THz beam focusing. Focusing performance was investigated by measuring Gaussian beam intensity distribution in the focal plane and along the optical axis of the lens. The beam waist and the focal depth for each MPFL were evaluated. The influence of the phase quantization number on the focused beam amplitude was estimated, and the power transmission efficiency reaching more than 90% was revealed. The THz imaging of less than 1 mm using a robust 50 mm diameter multilevel THz lens was achieved and demonstrated at 580 GHz frequency.

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Laser processing for precise fabrication of the THz optics

Cited by 10 publications

References 10 publications

The Magic of Optics—An Overview of Recent Advanced Terahertz Diffractive Optical Elements

The Magic of Optics—An Overview of Recent Advanced Terahertz Diffractive Optical Elements

Laser-Ablated Silicon in the Frequency Range From 0.1 to 4.7 THz

Compact diffractive optics for THz imaging

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