Phase-Matching in Nonlinear Optical Compounds: A Materials Perspective

Abstract

Angle phase-matching in nonlinear optical (NLO) materials is critical for technological applications. The purpose of this manuscript is to describe the concept of phase-matching for the materials synthesis NLO community. Refractive index and birefringence are defined with respect to uniaxial and biaxial crystal systems. The phase-matching angle and wavelength range, Type I and Type II, are explained using real NLO materials, K 3 B 6 O 10 Cl (KBOC) and Ba 3 (ZnB 5 O 10 )PO 4 (BZBP) In addition, we describe how refractive index measurements are performed on single crystals and how the resulting birefringence impacts the phase-matching. Our goal is to provide a description of phase-matching that is relevant for the materials synthesis NLO community.

CsB4O6F: A Congruent‐Melting Deep‐Ultraviolet Nonlinear Optical Material by Combining Superior Functional Units

“…As n z Àn y < n y Àn x ,i td epicts that CBF is an egative biaxial crystal, and the birefringence, Dn = n z Àn x ,is0.10826-0.12738 over the measured range.W ith the help of the chromatic dispersion curves,w ec an evaluate the DUV PM ability of CBF. [17] Therelation of PM angles (q m , f m )with respect to the second-harmonic wavelength is shown in Figure 2f.I ti sa lso possible to determine the shortest PM wavelength by extrapolating the minimal value of the curves,t othe Y-axis. ForC BF,t he shortest PM second-harmonic wavelength is down to 171.6 nm, and 211.5 nm in XY plane,f or type Ia nd type II, respectively.C ompared with other NLO materials, CBF processes an outstanding DUV PM capability,w hich is one of the few NLO crystals that can generate DUV coherent light below 200 nm by ad irect SHG process.…”

Two Novel Deep‐Ultraviolet Nonlinear Optical Crystals with Shorter Phase‐Matching Second Harmonic Generation than KBe2BO3F2: A First‐Principles Prediction

“…Therefore, in the field of deep‐UV laser technology one of the most important issues is to design new deep‐UV NLO materials with shorter SHG output wavelength and higher operating power than those of KBBF. The achievement of the phase‐matching condition is the key to solve this problem and guarantee a NLO output with a sufficient efficiency and suitable wavelength, which is a very important requirement for the practical NLO process . In this sense, many materials with large deep‐UV bandgaps and strong NLO effects actually cannot achieve an effective deep‐UV output, due to their weak phase‐matching abilities .…”

CsAlB3O6F: a beryllium-free deep-ultraviolet nonlinear optical material with enhanced thermal stability

“…6 The phase-matching ability is a key factor that should never be ignored for any practical DUV NLO application, which relies on both birefringence (Dn) and its dispersion of the crystal. 33 The calculated Dn of CABF is 0.091 at 1064 nm, large enough to satisfy DUV phase-matching ( Fig. S10 †).…”