BBO and BiBO are the most commonly used crystals for SPDC applications. A single-crystal configuration allows for the obtaining of time-correlated photons, and a double-crystal configuration (also known as a paired crystal) can be used for the generation of polarization-entangled photon pairs. Paired crystals are produced by optical contact, and have AR coatings on their input and output surfaces
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Description
Spontaneous Parametric Down-Conversion (SPDC) is a quantum optics phenomenon where a photon spontaneously splits into two lower-energy, entangled photons, adhering to energy and momentum conservation laws. This weak process is fundamental to many quantum optics experiments and applications, including interference studies, quantum cryptography, and quantum metrology.
Beta-Barium Borate (BBO) and Bismuth Triborate (BiBO) are the most commonly used crystals for Spontaneous Parametric Down-Conversion (SPDC) applications.
In a single-crystal configuration, these crystals can generate time-correlated photons. This configuration is particularly useful when the goal is to observe and measure the correlation between photons in terms of their arrival times.
For the generation of polarization-entangled photon pairs, a double-crystal configuration (also known as a paired crystal configuration) is employed. This setup involves the use of two identical crystals, which are aligned in such a way that the polarization state of the photons passing through the first crystal is entangled with the polarization state of the photons passing through the second crystal.
These paired crystals are typically produced using a process known as optical contact bonding, which allows for the creation of a monolithic structure without the need for any adhesive material. This ensures a high degree of alignment accuracy and stability.
To enhance the performance of these crystals and to minimize losses due to reflection, Anti-Reflection (AR) coatings are applied on both the input and output surfaces of the crystals. These coatings are designed to allow as much light as possible to pass through the crystal, thereby maximizing the efficiency of the photon generation process.
Specifications
Physical and Optical Properties
| Chemical formula | β-BaB2O4 (beta barium borate) |
| Optical symmetry | negative uniaxial (no > ne) |
| Crystal structure | trigonal |
| Lattice constants | a = 12.53 Å, c = 12.72 Å |
| Density | 3.85 g/cm3 |
| Mohs hardness | 4.5 |
| Melting point | 1095 °C |
| Refractive index (at 1064 nm) | no = 1.6551, ne = 1.5426 |
| Thermal conductivity coefficient | K⊥c = 1.2 Wm-1K-1, K//c = 1.6 Wm-1K-1 |
| Specific heat (298 K) | C = 0.49 Jg-1K-1 |
| Termal expansion coefficient (298 K) | α⊥c = 4 x 10-6 °C-1, α//c = 36 x 10-6 °C-1 |
| Thermo-optic coefficient (293-353 K) | dno/dT = -16.6 × 10-6 °C-1, dne/dT = -9.3 × 10-6 °C-1 |
| Direct band-gap energy (293 K) | Eg = 6.2 eV |
| Transparency range | 190 – 3500 nm |
| Chemical formula | BiB3O6 (bismuth triborate) |
| Optical symmetry | negative biaxial |
| Crystal structure | monoclinic |
| Lattice constants | a = 7.12 Å, b = 4.99 Å, c = 6.51 Å, β = 105.62° |
| Density | 5.03 g/cm3 |
| Mohs hardness | 5 – 5.5 |
| Melting point | 726 °C |
| Refractive index (at 1064 nm) | nx = 1.7565, ny = 1.7831, nz = 1.9161 |
| Thermal conductivity coefficient | K//x = 7.8 Wm-1K-1, K//y = 7 Wm-1K-1, K//z = 17.3 Wm-1K-1 |
| Specific heat (330 K) | C = 0.5 Jg-1K-1 |
| Termal expansion coefficient | α//x = 48 x 10-6 °C-1, α//y = 4.4 x 10-6 °C-1, α//z = -26.9 x 10-6 °C-1 |
| Direct band-gap energy (293 K) | Eg = 4.32 eV |
| Transparency range | 286 – 2500 nm |
Standard manufacturing specifications
| Cut orientation error: | +/- 30 arcmin |
| Dimensions tolerance: | +/- 0.1 mm |
| Clear aperture: | > 85% of aperture dimensions |
| Surface quality: | 10-5 S-D |
| Surface flatness: | < λ/10 @ 633 nm |
| Parallelism error: | < 20 arcsec |
| Perpendicularity error: | +/- 5 arcmin |
Products
Product | Dimensions | Length | Mount | Theta | Phi | Coatings | Price | Delivery | Quantity | ||
|---|---|---|---|---|---|---|---|---|---|---|---|
BBO-SPDC-P405-T1-5x5x2 | 5 x 5 mm | 2 mm | - | 29.2° | 90° | AR/AR 405+810 nm | 636.00$ | 2-4 weeks | |||
BBO-SPDC-P405-T1-5x5x3 | 5 x 5 mm | 3 mm | - | 29.2° | 90° | AR/AR 405+810 nm | 636.00$ | 2 weeks |
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