We propose a guided-mode-resonance (GMR) approach to evanescent-wave interference lithography that overcomes the severe depth of field and proximity limitations of conventional near-field methods. The scheme consists of a resonant dielectric grating and a photoresist layer separated by a low-index buffer medium, where phase-matched evanescent coupling transfers resonantly enhanced standing-wave fields from the grating to the photoresist. Using rigorous coupled-wave analysis, we design a UV-compatible structure comprising HfO 2 grating ridges, a commercial photoresist layer, and a transparent immersion-oil spacer. An example device supports two coupled GMR states near 365 nm that generate subwavelength interference fringes with a period of 120 nm, corresponding to approximately λ/3. Enhanced field localization in the photoresist produces peak intensities of ~600× the incident intensity while maintaining fringe visibility of ~0.999. The resonances remain robust for practical incidence-angle and grating–photoresist spacing variations, including a 1-µm separation compatible with conventional lithographic processing. The large resonant enhancement can reduce exposure times by nearly three orders of magnitude or equivalently lower required laser power. These results establish guided-mode-resonance field transfer as a potential route toward high-resolution, low-power evanescent-wave interference lithography using all-dielectric structures.
We demonstrate an optimized cascaded χ (3) – χ (2) source for picosecond mid-infrared pulse generation at 3.34 µm. A 1064 nm Yb-fiber master oscillator power amplifier system pumps a photonic crystal fiber (PCF) to generate a weak Stokes seed at 1.56 µm via four-wave mixing (FWM), which, together with residual pump light, pumps and seeds optical parametric amplification (OPA) in an MgO-doped PPLN crystal. We empirically maximize the OPA idler conversion efficiency by performing a systematic cutback of the PCF to optimize the Stokes seed power relative to the residual pump power. The optimum PCF length of 0.15 m has only 0.03% FWM Stokes conversion and generates 98 mW of idler power (196 nJ pulse energy) at 3.34 µm, with a conversion efficiency of 9.8%. These results show that low-conversion FWM provides an effective self-synchronized seed for compact fiber-pumped mid-infrared parametric sources.
This Letter presents the first, to the best of our knowledge, use of the Nd:YAG fifth harmonic for quantitative absorption line broadening measurements via frequency-scanning planar laser-induced fluorescence (FS-PLIF). This measurement is performed in a combustion environment generated with an oxy-propane torch. Using a harmonic of the Nd:YAG for PLIF removes the need for complex wavelength conversion equipment and greatly simplifies the optical setup while providing higher pulse energies than other conventional systems. Frequency scanning is performed for measurement rates of up to 20 kHz with a 500 kHz laser repetition rate and an average pulse energy of 1.7 mJ at 213 nm. The measured average linewidth of absorption features equals 0.366 cm −1 , corresponding to an estimated temperature of 2200 K. Predicted 2D temperature profiles show good agreement with CFD-simulated results.
