Phase-Insensitive Scattering of Terahertz Radiation

At a Glance

Metadata	Details
Publication Date	2017-01-31
Journal	Photonics
Authors	Mihail Petev, Niclas Westerberg, E. Rubino, Daniel Moss, A. Couairon
Institutions	Centre National de la Recherche Scientifique, Centre de Physique Théorique
Citations	5
Analysis	Full AI Review Included

Technical Documentation & Sales Analysis: Phase-Insensitive Scattering of Terahertz Radiation in MPCVD Diamond

This document analyzes the research paper “Phase-Insensitive Scattering of Terahertz Radiation” to provide technical specifications and align the material requirements with 6CCVD’s high-purity MPCVD diamond capabilities, focusing on driving sales to researchers in nonlinear optics and THz detection.

Executive Summary

This study successfully demonstrates a novel mechanism for frequency up-conversion of Terahertz (THz) radiation into the Ultraviolet (UV) spectrum using high-intensity Near-Infrared (NIR) pulses within Single Crystal Diamond (SCD).

Core Application: Detection and frequency up-conversion of THz radiation using nonlinear mixing in a solid-state medium.
Material Choice: A 500 µm thick, (100)-cut Single Crystal Diamond (SCD) sample was selected due to its exceptional optical transparency across the THz, NIR, and UV spectral regions.
Key Achievement: Observation of a distinct UV emission peak at ~430 nm, corresponding to the frequency-shifted THz seed pulse.
Novel Mechanism: The ~430 nm signal is confirmed to originate from Phase-Insensitive Scattering (PI) of the THz seed off the refractive index perturbation (shock front) induced by the intense NIR pump pulse.
Contrast to EFISH: This PI scattering provides a phase-insensitive alternative to the traditional Electric Field-Induced Second Harmonic (EFISH) process for THz detection.
High-Intensity Regime: The experiment required high-intensity NIR pump pulses (up to 10 µJ, 40 fs) to induce the necessary nonlinear effects (self-steepening and supercontinuum generation) for efficient PI scattering.

Technical Specifications

The following hard data points were extracted from the experimental setup and results:

Parameter	Value	Unit	Context
Material Substrate	Single Crystal Diamond (SCD)	N/A	(100)-cut orientation.
SCD Thickness	500	µm	Sample dimension used for nonlinear mixing.
NIR Pump Wavelength	790	nm	Central wavelength of the intense pump pulse.
NIR Pump Duration	40	fs	Full-width at half-maximum.
NIR Pump Energy (High)	10	µJ	Energy required to observe Phase-Insensitive Scattering (PI).
THz Seed Frequency	~5	THz	Carrier frequency (~60 µm wavelength).
THz Seed Duration	~90	fs	Single cycle sine wave pulse.
THz Seed Energy	~1	µJ	Input energy of the weak seed pulse.
Phase-Insensitive Scattering Peak	~430	nm	UV emission peak resulting from PI scattering.
EFISH Peak (Second Harmonic)	~395	nm	Expected second harmonic wavelength.
Nonlinear Refractive Index (n₂)	1.2 x 10^-15	cm²/W	Value used in numerical modeling.
Shock Front Velocity (v_p)	0.1223	µm/fs	Velocity of the scattering potential (refractive index perturbation).

Key Methodologies

The experiment relied on precise temporal and spatial overlap of high-intensity NIR and THz pulses within the SCD crystal.

NIR Pump Generation: 790 nm, 40 fs pulses delivered at a 100 Hz repetition rate by a Ti:sapphire laser system.
THz Seed Generation: Broadband THz seed generated via two-color gas ionization (1.8 µm pump and its second harmonic).
THz Filtering: The THz beam was filtered using gold mesh long pass filters (cutoff at 20 THz) providing >10⁴ isolation to remove high-frequency components and residual 1800 nm pump field.
Focusing and Overlap: The THz pulse was focused onto the SCD sample using a gold-coated, 90° off-axis parabolic mirror, achieving an ~85 µm width. The NIR pump was tightly focused and overlapped collinearly and temporally with the THz field inside the 500 µm SCD sample.
Detection: The resulting UV radiation was collected and measured using an imaging spectrometer (Newport MS260i) coupled to a CCD camera (QSI 620).
Numerical Validation: The results were validated using numerical simulations solving the nonlinear Maxwell’s equations via the Pseudospectral Space Domain (PSSD) algorithm and Coupled Nonlinear Envelope Equations (NEE) to isolate the Phase-Insensitive Scattering term (P_nl1).

6CCVD Solutions & Capabilities

The successful replication and extension of this research—particularly the reliance on high-quality, ultra-transparent SCD for high-intensity nonlinear interactions—is directly supported by 6CCVD’s core manufacturing expertise.

Applicable Materials

To replicate or extend this research into advanced THz-NIR nonlinear optics, 6CCVD recommends:

Optical Grade Single Crystal Diamond (SCD): Required for its extremely low absorption coefficient across the critical spectral range (THz, 790 nm NIR, and 430 nm UV). Our MPCVD SCD ensures the high purity necessary to minimize fluorescence and maximize the nonlinear interaction length.
Custom (100) Orientation: We provide SCD plates with precise crystallographic orientation, matching the (100)-cut used in the study, which is crucial for specific nonlinear processes.

Customization Potential

6CCVD’s advanced manufacturing capabilities allow researchers to optimize material parameters beyond the scope of the original paper:

Requirement from Research Paper	6CCVD Solution & Capability	Technical Advantage
Specific Thickness (500 µm)	Custom Thickness Control	We offer SCD plates from 0.1 µm up to 500 µm, and substrates up to 10 mm, allowing precise control over the interaction length for phase matching optimization.
High-Intensity Operation	Ultra-Low Roughness Polishing	Our SCD polishing achieves surface roughness of Ra < 1 nm. This is critical for minimizing scattering losses and increasing the laser-induced damage threshold (LIDT) under intense 10 µJ, 40 fs pump pulses.
Advanced Device Integration	Custom Metalization Services	If future experiments require integrated THz antennas or electrical biasing for enhanced EFISH or ABCD detection, 6CCVD offers in-house metalization (Au, Pt, Pd, Ti, W, Cu) patterning capabilities.
Larger Scale Experiments	Large Area PCD Capability	For scaling up THz detection arrays or high-power applications, we offer Polycrystalline Diamond (PCD) plates/wafers up to 125 mm in diameter, polished to Ra < 5 nm.

Engineering Support

6CCVD’s in-house PhD team specializes in the material science of diamond for extreme optical and electronic applications. We can assist with material selection, dispersion engineering, and surface preparation for similar THz frequency conversion and nonlinear optics projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

The nonlinear interaction between Near-Infrared (NIR) and Terahertz pulses is principally investigated as a means for the detection of radiation in the hardly accessible THz spectral region. Most studies have targeted second-order nonlinear processes, given their higher efficiencies, and only a limited number have addressed third-order nonlinear interactions, mainly investigating four-wave mixing in air for broadband THz detection. We have studied the nonlinear interaction between THz and NIR pulses in solid-state media (specifically diamond), and we show how the former can be frequency-shifted up to UV frequencies by the scattering from the nonlinear polarisation induced by the latter. Such UV emission differs from the well-known electric field-induced second harmonic (EFISH) one, as it is generated via a phase-insensitive scattering, rather than a sum- or difference-frequency four-wave-mixing process.

Tech Support

Original Source

DOI: https://doi.org/10.3390/photonics4010007

References

2005 - THz imaging and sensing for security applications—Explosives, weapons and drugs [Crossref]
2009 - Laser-based standoff detection of explosives: A critical review [Crossref]
2007 - Cutting-edge terahertz technology [Crossref]
1996 - Optical second-harmonic probe for silicon millimeter-wave circuits [Crossref]
1998 - Detection of freely propagating terahertz radiation by use of optical second-harmonic generation [Crossref]
2006 - Detection of Broadband Terahertz Waves with a Laser-Induced Plasma in Gases [Crossref]
2008 - Coherent heterodyne time-domain spectrometry covering the entire “terahertz gap” [Crossref]
2013 - Spectrally resolved wave-mixing between near- and far-infrared pulses in gas [Crossref]
2015 - Broadband field-resolved terahertz detection via laser induced air plasma with controlled optical bias [Crossref]