The BXT2 series is Opto Diode’s family of two-stage cooled, single-channel lead selenide (PbSe) infrared detectors, part of the B Series of high-performance PbSe devices. Built for the 1–5 micron (mid-wave infrared) region, the BXT2 detectors pair high sensitivity and the fast response that PbSe is known for with thermoelectric two-stage cooling — which lowers the element operating temperature for greater detectivity and added stability when ambient temperatures fluctuate.
If you’ve been searching a specific part number — BXT2-17T, BXT2-17TF, BXT2-27, BXT2-37T, BXT2S-28T, BXT2S-38T, or BXT2S-68TE — this is the canonical Opto Diode page for the series, with specifications drawn directly from the B Series datasheet.
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Why the BXT2 Series
- Two-stage cooling. BXT2 devices reach element operating temperatures from roughly −30 °C to −45 °C, providing additional sensitivity for very low-level signal detection and enhanced stability where temperatures are in constant flux.
- Mid-IR coverage. PbSe responds across the 1–5 µm spectrum, with peak sensitivity wavelength near 4.1–4.7 µm depending on model — the band most useful for many gas, combustion, and thermal measurements.
- Fast response. PbSe offers the fastest response speed among Opto Diode’s lead-salt detectors; BXT2 typical time constants are in the 8–12 µs range.
- High detectivity. D* (λp, 1000 Hz, 1 Hz) reaches up to 3.5×10¹⁰ cm·Hz¹ᐟ²·W⁻¹ (typical, BXT2S models).
- US-made. Designed and manufactured by Opto Diode in Camarillo, California — a division of ITW — with over 25 years of PbS/PbSe detector manufacturing experience and full support for custom requirements.
BXT2 Series Specifications
| Model | Part # | Element size | Package | Active area (mm²) | Element op. temp (°C) | Peak λp (µm), min–typ | D* λp (cm·Hz¹ᐟ²·W⁻¹) | Time constant (µs), typ–max | Window |
|---|---|---|---|---|---|---|---|---|---|
| BXT2-17T | 40174 | 1 × 1 mm | TO37 | 1 | −35 | 4.1–4.3 | 1.6×10¹⁰ | 8–14 | Flat Sapphire |
| BXT2-17TF | 40065 | 1 × 1 mm | TO37 | 1 | −30 | 4.3–4.7 | 2.4×10¹⁰ | 8–14 | 4.7 µm Bandpass Si Filter |
| BXT2-27 | 40587 | 2 × 2 mm | TO37 | 4 | −30 | 4.1–4.3 | 1.8×10¹⁰ | 8–14 | Flat Sapphire |
| BXT2-37T | 40071 | 3 × 3 mm | TO37 | 9 | −35 | 4.1–4.3 | 1.6×10¹⁰ | 8–14 | Flat Sapphire |
| BXT2S-28T | 40186 | 2 × 2 mm | TO8 | 4 | −45 | 4.3–4.5 | 2.0×10¹⁰ – 3.5×10¹⁰ | 12–25 | Flat Sapphire |
| BXT2S-38T | 40203 | 3 × 3 mm | TO8 | 9 | −45 | 4.3–4.5 | 2.0×10¹⁰ – 3.5×10¹⁰ | 12–25 | Flat Sapphire |
| BXT2S-68TE | 40076 | 6 × 6 mm | TO8 | 36 | −25 | 4.3–4.5 | 1.5×10¹⁰ | 12–25 | Flat Sapphire |
Storage and operating temperature range: −40 °C to +85 °C. Specifications per the B Series datasheet; verify against the controlling datasheet revision before design-in. View the full B Series IR Detectors datasheet (PDF).
The “S” variants (BXT2S-28T, BXT2S-38T, BXT2S-68TE) use the TO8 package and reach the coldest element temperatures (−45 °C on the 28T/38T) for the highest detectivity in the series. The BXT2-17TF is supplied with an integrated 4.7 µm bandpass Si filter for applications that need in-band selection without a separate optic.
Applications
Per the B Series datasheet, these detectors are applied to:
- Gas analysis — medical and industrial
- Emissions monitoring
- Spectroscopy
- Process control systems
- Thermal imaging
- Defense and security
Packaging
BXT2 detectors ship in hermetic TO37 and TO8 metal packages with integrated thermoelectric coolers and thermistors for closed-loop temperature control. See the datasheet for package dimensions and pin-outs.
Where BXT2 Fits in the PbSe Line
BXT2 is the two-stage cooled tier of Opto Diode’s PbSe family. For warmer-running or cost-sensitive designs, the uncooled (BXP) and one-stage cooled (BXT1) options share the same 1–5 µm PbSe technology. Browse the full PbSe detector line, or — if you’re still deciding between PbS and PbSe — see our PbS vs PbSe selection guide.
Request a Quote or Datasheet
Specifying a two-stage cooled PbSe detector for a gas analyzer, emissions monitor, or mid-IR instrument? Tell us your target wavelength, element size, and cooling and packaging needs, and our engineers will recommend the right BXT2 configuration — or a custom design.
[Contact Opto Diode for BXT2 pricing, datasheets, and custom detectors →](https://optodiode.com/contact-us/)
Frequently Asked Questions
What wavelength range do BXT2 detectors cover?
The BXT2 PbSe detectors respond across the 1–5 µm mid-wave infrared region, with a peak sensitivity wavelength near 4.1–4.7 µm depending on the model.
What is the difference between BXT2 and BXT2S models?
Both are two-stage cooled. The “S” models (BXT2S-28T, BXT2S-38T, BXT2S-68TE) use the TO8 package; the BXT2S-28T and BXT2S-38T reach the coldest element operating temperature in the series (−45 °C) for the highest detectivity.
Which BXT2 model has the largest active area?
The BXT2S-68TE offers a 6 × 6 mm element (36 mm² active area) in a TO8 package.
Are BXT2 detectors made in the USA?
Yes — Opto Diode designs and manufactures its PbSe detectors in Camarillo, California, as a division of ITW, with over 25 years of lead-salt detector manufacturing experience and support for custom requirements.