Direct writing of 150 nm gratings and squares on ZnO crystal in water by using 800 nm femtosecond laser

Abstract

We present a controllable fabrication of nanogratings and nanosquares on the surface of ZnO crystal in water based on femtosecond laser-induced periodic surface structures (LIPSS). The formation of nanogrooves depends on both laser fluence and writing speed. A single groove with width less than 40 nm and double grooves with distance of 150 nm have been produced by manipulating 800 nm femtosecond laser fluence. Nanogratings with period of 150 nm, 300 nm and 1000 nm, and nanosquares with dimensions of 150 × 150 nm² were fabricated by using this direct femtosecond laser writing technique.

Competition between subwavelength and deep-subwavelength structures ablated by ultrashort laser pulses

“…By using Eqs. (5)- (8), the N SPI , N TPI , and the total excited electron concentration N eh with laser fluence were iteratively calculated [ Fig. 6(a)].…”

“…The period of the formed structure is typically larger than halfwavelength, λ∕2, with a strong dependence on the angle of incidence [4,5]. However, under femtosecond (fs) laser irradiation, periods slightly smaller than the laser wavelength [therefore, subwavelength structures (SWS)] [3,4], as well as deep-subwavelength structures (DSWS) [6][7][8][9][10][11] with periods considerably smaller than λ∕2, were observed on transparent materials and semiconductors. Up to now, these two types of surface structures have become a universally observed feature in the fs laser multipulse ablation [3][4][5].…”

Progress in ultrafast laser processing and future prospects

“…Further reduction to a level very near to the ablation threshold results in only a single cycle of the modulated energy distribution in the central area of the focal volume ( Fig. 7(c)), which creates a single line nanogroove [53][54][55][56]. Using this scheme, an array of single nanogrooves with widths less than 40 nm were fabricated on ZnO, as shown in the SEM image of Fig.…”

“…Using this scheme, an array of single nanogrooves with widths less than 40 nm were fabricated on ZnO, as shown in the SEM image of Fig. 8(a) [56]. To write a single groove line, the focused laser beam was scanned along the direction perpendicular to the laser beam polarization.…”

Piecewise Linear Weighted Iterative Algorithm for Beam Alignment in Scanning Beam Interference Lithography

“…Periodic micro/nanostructures have numerous applications, such as photonic crystals [1], liquid crystal displays [2], solar cells [3,4], high density data storage [5,6], and biosensors [7,8]. A number of technologies have been utilized to fabricate periodic structures, including interference lithography [9], nanoimprinting [10,11], electron beam lithography [12,13], focused ion beam etching [14], and direct laser writing [15][16][17]. These commonly used techniques are difficult to produce large area micro/nanostructures with diameters of several hundred millimeters.…”