BBO crystals are among one the most functional nonlinear optical products for frequency conversion applications. They can create ultraviolet, visible, as well as near-infrared light from various laser sources, such as Nd: YAG, Ti: sapphire, as well as fiber lasers. BBO crystals have high nonlinear coefficients, a broad transparency range, low group-velocity diffusion, and a high damage threshold. Nevertheless, producing top-quality BBO crystals calls for mindful control of the crystal growth procedure and post-growth treatments.
This short article will explain how we generate high-grade BBO crystals at our company. We will likewise go over some advantages as well as obstacles to using BBO crystals for regularity conversion.
What is a BBO crystal?
BBO stands for beta-barium borate (β-BaB2O4), a birefringent crystal with a trigonal structure. It belongs to the 3m factor group with three major axes: X, Y, as well as Z. The Z-axis is parallel to the optical axis of the crystal as well as is additionally called the great axis. The X- as well as Y-axes, are perpendicular to the optical axis and also are called regular axes.
BBO crystals have 2 refractive indices: ne for amazing rays as well as no for ordinary rays. The difference between ne as well as no relies on the wavelength of light and also the temperature level of the crystal. This distinction causes phase inequality between different light polarization elements when propagating with a BBO crystal. Readjusting the angle between the beam as well as the crystal axes can compensate for this phase mismatch.
BBO crystals have large nonlinear coefficients that enable efficient frequency conversions processes such as second-harmonic generation (SHG), third-harmonic generation (THG), fourth-harmonic generation (FHG), fifth-harmonic generation (5HG), sum-frequency generation (SFG) as well as difference-frequency generation (DFG). These procedures entail blending two or even more input light beams with different regularities to generate a result beam with a brand-new regularity.
Just how Do We Grow BBO Crystals?
We grow BBO crystals by making use of a changed Czochralski technique with a platinum crucible. The raw products are barium carbonate (BaCO3) and also boric acid (H3BO3), combined in a stoichiometric proportion of 1:2. The blend is then thawed at concerning 1100 ° C under an oxygen atmosphere.
The seed crystal is a small BBO crystal with a well-defined alignment along its major axes. The seed crystal is affixed to a turning pole that dips into the thaw surface area. The rod is gradually brought up while rotating at a consistent rate. This creates a thin thaw layer to strengthen the seed crystal, developing a round boule.
The growth price depends on temperature level slope, rotation rate, pulling rate, melt composition, and oxygen pressure. We very carefully monitor these variables during the development procedure to ensure uniformity and also top quality of the boule.
The common dimension of our boule is about 50 mm in diameter and 100 mm in length. After growing, we anneal the boule at regarding 900 ° C for several hrs to soothe interior stress and boost optical homogeneity.
Just how Do We Cut and also Polish BBO Crystals?
We reduced our boule right into smaller pieces according to consumer requirements utilizing a ruby blade, or wire saw the device. After that polish these items making use of ruby powder or slurry on cast iron or copper plates.
The cutting angle depends on the desired phase-matching problem for regularity conversion applications. Stage matching describes matching the phase speeds of various beams of light associated with nonlinear procedures to ensure that they build up constructively over fars away inside the crystal.
There are 2 types of stage matching: critical stage matching (CPM) and also noncritical stage matching (NCPM). CPM happens when the input beam propagates along among the major axes of the crystal, such as the Z-axis, and its polarization is vertical to that axis, such as X- or Y-polarized. NCPM occurs when the input beam of light propagates at an angle aside from no or 90 levels concerning among the major axes, such as the Z-axis. Its polarization is parallel to that axis, such as Z-polarized.
For CPM, we reduced our items at an angle equal to no or 90 degrees worrying among the primary axes. For NCPM, we reduced our pieces at an angle identified by Snell’s law:
ni sin( ɵi) = no sin( ɵo) where ni as well as no are the refractive indices of the input and output media, respectively, and ɵi and ɵo are the angles of incidence and refraction, respectively.
We brighten our pieces making use of a fine-grained ruby powder or slurry on an actor’s iron or copper plate. We use uniform stress and movement to accomplish a smooth surface area with low roughness as well as high flatness. And also coat our items with anti-reflection layers to decrease representation losses at the crystal surface areas.
The normal dimension of our pieces varies from 1 mm to 25 mm in diameter or length. The surface area top quality is much better than 10-5 scratch-dig according to the MIL-PRF-13830B standard. The surface area flatness is much better than lambda/8 at 633 nm wavelength. The parallelism is better than 10 arc secs. The clear aperture is larger than 90% of the central area.
What Are the Benefits of Using BBO Crystals?
BBO crystals have several advantages for regularity conversion applications, such as:
High nonlinear coefficients: BBO crystals have large nonlinear coefficients that enable effective regularity conversion processes with reduced input power needs. As an example, BBO crystals have a nonlinear coefficient d31 of regarding 2 pm/V for SHG at 1064 nm wavelength, which is about 10 times larger than KDP crystals.
Broad transparency range: BBO crystals have a wide openness range from 189 nm to 3500 nm, covering ultraviolet, noticeable, and also near-infrared areas. This allows BBO crystals to be made use of for numerous laser resources with various wavelengths.
Low group-velocity dispersion: BBO crystals have reduced group-velocity diffusion (GVD) that lessens the temporal expansion of ultrashort pulses during frequency conversion procedures. For example, BBO crystals have a GVD specification β2 of regarding -35 fs ^ 2/mm for SHG at 800 nm wavelength, about two orders of size smaller sized than KDP crystals.
High damages limit: BBO crystals have high damages limits that can hold up against high tops as well as ordinary power without deterioration or damage. For instance, BBO crystals have a damage threshold of regarding 10 GW/cm ^ 2 for SHG at 1064 nm wavelength with a 10 ns pulse period, regarding five times more than KDP crystals.
What Are the Challenges of Using BBO Crystals?
BBO crystals additionally have some obstacles for regularity conversion applications, such as:
Tiny approval angle: BBO crystals have a little approval angle that limits the input light beam’s light beam divergence as well as setting high quality for efficient frequency conversion. For instance, BBO crystals have an approval angle of about 0.8 mrad-cm for SHG at 1064 nm wavelength, which is about four times smaller than that of KDP crystals.
Big angular walk-off BBO crystals have a big angular walk-off that creates spatial splitting up between different polarization parts of light when propagating through a BBO crystal. This decreases the effective interaction length and also lowers the conversion efficiency. As an example, BBO crystals have an angular walk-off of regarding 38 mrad for SHG at 1064 nm wavelength, which has to do with 6 times larger than KDP crystals.
Temperature sensitivity: BBO crystals’ temperature sensitivity impacts their refractive indices as well as phase-matching conditions. This needs temperature level stabilization or adjusting devices to keep ideal efficiency. For instance, BBO crystals have a temperature bandwidth of concerning 55 ° C-cm for SHG at 1064 nm wavelength, about 3 times smaller than KDP crystals.
Just how Do We Check Our BBO Crystal Products?
We test our BBO crystal items by utilizing different techniques, such as:
X-ray diffraction (XRD): We make use of XRD to gauge our boules and also items’ crystal structure and positioning. We ensure that our items are pure beta-phase without alpha-phase contamination or twinning defects.
Optical transmission (OT): We make use of OT to gauge the optical passage range of our pieces over their transparency range. We ensure our items are without absorption bands or scattering losses because of contaminations or problems.
Second harmonic generation (SHG): We make use of SHG to determine our pieces’ nonlinear conversion performance and phase-matching angle for a given input wavelength. We make certain that our products satisfy the specifications for SHG applications.
Third harmonic generation (THG): We use THG to gauge our pieces’ nonlinear conversion performance and phase-matching angle for an offered input wavelength. We make certain that our items satisfy the requirements for THG applications.
Optical parametric oscillation (OPO): We utilize OPO to determine our items’ nonlinear conversion effectiveness as well as phase-matching angle for a provided input wavelength as well as signal/idler wavelengths. We ensure that our items fulfill the requirements for OPO applications.
Optical parametric amplification (OPA): We use OPA to determine our items’ nonlinear conversion effectiveness and also phase-matching angle for a given input wavelength and signal/idler wavelengths. We ensure that our products satisfy the specifications for OPA applications.
Optical parametric chirped-pulse amplification (OPCPA): We use OPCPA to determine our pieces’ nonlinear conversion effectiveness as well as phase-matching angle for an offered input wavelength and also signal/idler wavelengths. We likewise determine the enhanced pulses’ temporal pulse form and spectral bandwidth. We make sure that our items fulfill the requirements for OPCPA applications.
What Are Some Instances of BBO Crystal Applications?
BBO crystals have lots of applications in numerous areas, such as:
Laser science: BBO crystals are extensively made use of for regularity conversion processes such as SHG, THG, OPO, OPA, and OPCPA to create ultraviolet, visible, or near-infrared light from various laser resources. For example, BBO crystals can produce 266 nm light from 1064 nm Nd: YAG lasers or 400 nm light from 800 nm Ti: sapphire lasers.
Nonlinear optics: BBO crystals are likewise used for other nonlinear optical procedures such as sum-frequency generation (SFG), difference-frequency generation (DFG), optical rectification (OR), electro-optic modulation (EOM), as well as Pockels effect. For instance, BBO crystals can produce terahertz radiation from OR or modulate laser light beams with EOM.
Quantum optics: BBO crystals serve for quantum optical experiments such as knotted photon pair generation, quantum state tomography, quantum cryptography, as well as quantum assessment. For instance, BBO crystals can produce polarization-entangled photon sets from SPDC or perform quantum interference dimensions with the Hong-Ou-Mandel result.
Exactly How Can I Order Your BBO Crystal Products?
You can get our BBO crystal products by contacting us through email or phone. You can likewise visit our internet site to surf our catalog and also demand a quote online. We offer competitive rates and also rapid distribution worldwide. I appreciate your passion for our BBO crystal products!
