arXiv subjects

David J. Michaelis

Publications and source records attributed to David J. Michaelis.

6 recordsLinked to original sources

arXiv2026

ZPAN: An Organic Nonlinear Optical Crystal for High Intensity THz Generation

We report an optimized synthesis and crystal growth protocol as well as structural, optical, and terahertz (THz) generation characteristics of the organic nonlinear optical crystal ZPAN ((Z)-1-(((4-Phenylamino)phenylamino)methylene)naphthalen-2(1H)-one). Noncentrosymmetric packing of ZPAN is most reliably achieved by slow evaporation from an acetone-based solvent system, producing long rectangular prisms (7 cm \times 1 cm \times 0.2 cm) with (010) as the main face and [001] as both the polar axis and the direction of elongated crystal growth. [001] is thus the most effective pump polarization direction for generating THz light via optical rectification. The THz generation characteristics of the developed ZPAN crystals are determined at different near-infrared irradiation wavelengths, crystal thicknesses, and pump powers, revealing that ZPAN can generate a peak-to-peak electric field of near 1 MV/cm with a smooth spectrum from 0.5-3.4 THz. Calculated second order nonlinear optical coefficients indicate that both the (100) and (010) faces are theoretically capable of THz generation, though (010) is consistently the dominant growth face. The large size of this face (7 cm \times 1 cm) makes it possible to scale laser power with aperture size, for use in extremely high-power laser systems.

physics.optics↗

arXiv2024

High-Dynamic Range Broadband Terahertz Time-Domain Spectrometer Based on Organic Crystal MNA

We present a high power and broadband THz-TDS setup utilizing the nonlinear organic crystal MNA both as emitter and detector. The THz source is based on optical rectification of near infra-red laser pulses at a central wavelength of 1036 nm from a commercial, high-power Yb-based laser system and reaches a high THz average power of 11 mW at a repetition rate of 100 kHz and a broad and smooth bandwidth of more than 9 THz. The conversion efficiency is high (0.13%) in spite of the high excitation average power of 8 W. We validate the high dynamic range and reliability of the source for applications in linear spectroscopy by measuring the broadband THz properties of chi(2) nonlinear crystals up to 8 THz. This new high-repetition rate source is very promising for ultra-broadband THz spectroscopy at high dynamic range and/or reduced measurement times.

physics.optics↗

arXiv2022

A new standard in high-field terahertz generation: the organic nonlinear optical crystal PNPA

We report the full characterization of a new organic nonlinear optical (NLO) crystal for intense THz generation: PNPA ((E)-4-((4-nitrobenzylidene)amino)-N-phenylaniline). We discuss crystal growth and structural characteristics. We present the wavelength dependence of THz generation, the thickness dependence of the THz spectrum for PNPA crystals, and measure the efficiency. PNPA enables intense THz generation that surpasses NLO crystals DAST and OH-1, which have been the standard in organic high-field THz generators for several years.

physics.optics↗

arXiv2021

Data Mining for Terahertz Generation Crystals

We demonstrate a data mining approach to discover and develop new organic nonlinear optical crystals that produce intense pulses of terahertz radiation. We mine the Cambridge Structural Database for non-centrosymmetric materials and use this structural data in tandem with density functional theory calculations to predict new materials that efficiently generate terahertz radiation. This enables us to (in a relatively short time) discover, synthesize, and grow large, high-quality crystals of four promising materials and characterize them for intense terahertz generation. In a direct comparison to the current state-of-the-art organic terahertz generation crystals, these new materials excel. The discovery and characterization of these novel terahertz generators validates the approach of combining data mining with density functional theory calculations to predict properties of high-performance organic materials, potentially for a host of exciting applications.

cond-mat.mtrl-sci↗

arXiv2020

Enabling High-Power, Broadband THz Generation with 800-nm Pump Wavelength

The organic terahertz (THz) generation crystal BNA has recently gained traction as a valuable source to produce broadband THz pulses. Even when pumped with 800-nm light, thin BNA crystals can produce relatively high electric fields with frequency components out to 5 THz. However, the THz output when pumped with 800-nm light is limited by the damage threshold of the organic crystal. Here we report that the damage threshold of BNA can be significantly improved by physically bonding BNA to a high-thermal conductivity sapphire window. When pumped with 800-nm light from an amplified Ti:sapphire laser system, our bonded BNA (BNA-sapphire) generates 2.5 times higher electric field strengths compared to bare BNA crystals. We characterize the average damage threshold for bare BNA and BNA-sapphire, measure peak-to-peak electric field strengths and THz waveforms, and determine the nonlinear transmission in BNA. Pumping BNA-sapphire with 800-nm light results in peak-to-peak electric fields exceeding 1 MV/cm, with strong broadband frequency components from 0.5-5 THz. Our BNA-sapphire THz source is a promising alternative to tilted pulse front LiNbO3 THz sources, which will enable many research groups without optical parametric amplifiers to perform high-field, broadband THz spectroscopy.

physics.optics↗

arXiv2020

Comprehensive Characterization of Terahertz Generation with the Organic Crystal BNA

We characterize the terahertz (THz) generation of N-benzyl-2-methyl-4-nitroaniline (BNA), with crystals ranging in thickness from 123-700 μm. We compare excitation using 800-nm and 1250 to 1500-nm wavelengths. Pumping BNA with 800-nm wavelengths and longer near-infrared wavelengths results in a broad spectrum, producing out to 6 THz using a 100-fs pump, provided the BNA crystal is thin enough. ~200 μm or thinner crystals are required to produce a broad spectrum with an 800-nm pump, whereas ~300 μm thick crystals are optimal for broadband THz generation using the longer wavelengths. We report the favorable THz generation and optical characteristics of our BNA crystals that make them attractive for broadband, high-field THz generation, and we also find significant differences to BNA results reported in other works.

physics.optics↗