BGSe Crystal
WaveQuanta

BGSe (BaGa4Se7) Nonlinear Crystal for Mid-IR, 0.47–18 µm, d11 = 24 pm/V

WQ-NLC-BGSE
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BGSe (BaGa4Se7) is the selenide analogue of BaGa4S7 and a comparatively new mid-infrared nonlinear crystal, grown by the Bridgman–Stockbarger technique. It transmits from 0.47 to 18 µm, apart from an absorption peak near 15 µm, and combines a nonlinear coefficient of d11 = 24 pm/V with a surface damage threshold of 557 MW/cm² at 1.064 µm. WaveQuanta supplies BGSe as oriented blanks, polished elements and coated elements for OPO, OPA and DFG with pump sources from 1 to 3 µm.

Note: BGSe is a newly developed crystal and individual pieces may contain a few internal streaks. These do not affect stable performance, and returns are not accepted on the grounds of such streaks.

Key Features

  • Transmission range 0.47–18 µm, with an absorption peak near 15 µm
  • Nonlinear coefficient d11 = 24 pm/V; powder SHG response about 2–3 times that of AgGaS2
  • Surface damage threshold 557 MW/cm² at 1.064 µm (5 ns), about 3.7 times that of AgGaS2 under the same conditions
  • Accepts pump sources from 1 to 3 µm, with tunable output over 3–18 µm
  • Thermal expansion with low anisotropy: 9.24–11.70 × 10⁻⁶ /K along the three axes
  • About 65% transmittance over 1–14 µm through a polished 2 mm thick (001) plate
  • Shows terahertz phonon-polaritons and is studied for THz generation

Typical Applications

  • Mid-IR OPO and OPA pumped at 1–3 µm
  • Difference-frequency generation (DFG) for tunable 3–18 µm output
  • Intracavity and extracavity frequency conversion, with CW or pulsed pumping
  • Terahertz generation research

Standard Sizes

Size Cut / orientation Surface / coating Mount
3 × 3 × 5 mm θ = 42°, φ = 0° Blank Unmounted
3 × 7 × 15 mm θ = 40.5°, φ = 0° Blank Unmounted
3 × 7 × 20 mm θ = 40.5°, φ = 0° Blank Unmounted
3 × 7 × 30 mm θ = 40.5°, φ = 0°, Type I, XZ-cut S1: AR @ 1–1.5 µm (R < 0.2%); S2: HT @ 10–16 µm + 1–1.5 µm (R < 4%) Unmounted
5 × 5 × 1 mm θ = 40.5°, φ = 0° S1: AR @ 1–3 µm; S2: AR @ 3–20 µm Unmounted
5 × 5 × 1.5 mm θ = 40.5°, φ = 0° Blank Unmounted
5 × 5 × 1.5 mm θ = 40.5°, φ = 0° S1: AR @ 1–3 µm; S2: AR @ 3–20 µm Unmounted
5 × 5 × 2 mm θ = 40.5°, φ = 0° Blank Unmounted
5 × 5 × 2 mm θ = 40.5°, φ = 0° S1: AR @ 1–3 µm; S2: AR @ 3–20 µm Unmounted
5 × 5 × 3 mm θ = 60°, φ = 0° Polished, uncoated Unmounted
5 × 5 × 4 mm θ = 60°, φ = 0° Blank Unmounted
5 × 6 × 5 mm θ = 10°, φ = 90° Blank Unmounted
7 × 7 × 2 mm θ = 44°, φ = 0° Blank Unmounted
7 × 7 × 2 mm θ = 44°, φ = 0°, XZ-cut S1: HT @ 1.4–2.3 µm; S2: HT @ 5–9 µm Unmounted
7.2 × 6.4 × 2.3 mm θ = 47°, φ = 0° Blank Unmounted
7.2 × 6.4 × 3.3 mm θ = 47°, φ = 0° Blank Unmounted
10 × 10 × 1 mm θ = 43°, φ = 0° Polished, uncoated Unmounted

Availability of individual sizes changes; custom sizes, cut angles and coatings are available on request.

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Model: WQ-NLC-BGSE · Custom sizes, orientations and coatings on request — contact WaveQuanta for a quote and lead time.

Chemical Formula BaGa4Se7
Space Group Pc
Transmission Range 0.47–18 µm (absorption peak near 15 µm)
Transmittance ≈65% over 1–14 µm (polished 2 mm thick (001) plate)
Nonlinear Coefficient d11 = 24 pm/V
Birefringence at 2 µm 0.07
Surface Damage Threshold 557 MW/cm² (1.064 µm, 5 ns, 1 Hz, 0.4 mm spot)
Thermal Expansion Coefficients αa = 9.24 × 10⁻⁶ /K, αb = 10.76 × 10⁻⁶ /K, αc = 11.70 × 10⁻⁶ /K
Thermal Conductivity (298 K) 0.74 / 0.64 / 0.56 W/(m·K) along a / b / c
Thermal Diffusivity (298 K) 0.50 / 0.42 / 0.38 mm²/s along a / b / c
Pump Wavelength Range 1–3 µm
Tunable Output Range 3–18 µm
Dimension Tolerance (W ±0.1 mm) × (H ±0.1 mm) × (L +1 mm/−0.5 mm)
Clear Aperture > 90% central area
Flatness λ/8 @ 633 nm (T ≥ 1 mm)
Surface Quality 60-40 scratch-dig (after coating)
Parallelism Better than 30″
Perpendicularity 10′
Orientation Accuracy < 30″
Specification Sheet PDF — Download
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