Opto Diode’s B Series lead selenide (PbSe) detectors deliver fast, high-sensitivity response across the 1–5 µm mid-wave infrared band. Compare all three families — and their detectivity, responsivity, active areas and cooling — before downloading the datasheet or requesting a quote.
Which PbSe Series Do You Need?
All three share the same PbSe sensing element — cooling is the ladder that trades cost for sensitivity:
Uncooled · TO5
BXP
D* typ 1.5–2.0 × 10¹⁰
- Simplest path to MWIR sensing
- 1, 4, 9 mm² · sapphire, ARSi or 2.4 µm longpass Ge filter
- Gas analysis, flame detection, process monitoring
1-stage TE cooled · TO8/TO37
BXT1
D* typ 2.8 × 10¹⁰
- Lifts typical D* to 2.8 × 10¹⁰ (vs 1.5–2.0 × 10¹⁰ uncooled)
- 4, 9 mm² · peak shifts to 4.0–4.2 µm
- Stability in fluctuating temperatures
2-stage TE cooled · TO37/TO8
BXT2
D* typ up to 3.5 × 10¹⁰ (BXT2S)
- Family’s highest detectivity & longest peaks (4.1–4.5 µm)
- 1, 4, 9, 36 mm² — largest element in the line
- Low-signal, demanding measurements
Series Comparison
| Series | Type | Package | Active Areas | Peak Sensitivity | Element Temp | Window / Filter |
|---|---|---|---|---|---|---|
| BXP | Uncooled, packaged | TO5 | 1, 4, 9 mm² | 3.6–3.8 µm | +23 °C (ambient) | Flat sapphire, ARSi, or 2.4 µm longpass Ge |
| BXT1 | 1-stage TE cooled | TO8 / TO37 | 4, 9 mm² | 4.0–4.2 µm | −25 °C | Flat sapphire |
| BXT2 | 2-stage TE cooled | TO37 (BXT2) / TO8 (BXT2S) | 1, 4, 9, 36 mm² | 4.1–4.5 µm¹ | −25 to −45 °C by part | Flat sapphire; 4.7 µm bandpass Si on BXT2-17TF |
¹ The bandpass-filtered BXT2-17TF is specified at 4.3–4.7 µm. Spectral response spans roughly 1–5 µm across the family; cooling shifts the peak and cutoff longer. Storage & operating rating: −40 to +85 °C for all parts. Contact us for custom sizes.
Detectivity (D*) and Responsivity
D* is the primary figure of merit (cm·Hz½·W⁻¹, specified at peak wavelength and 1000 Hz); responsivity is in V/W. Cooling materially improves both:
| Series | D* (cm·Hz½·W⁻¹) | Responsivity (V/W) | Time Constant (typ/max) |
|---|---|---|---|
| BXP | min 2.65 × 10⁹ – 1.0 × 10¹⁰ · typ 1.5 – 2.0 × 10¹⁰ | typ 1.0 × 10⁴ – 3.0 × 10⁴ | 2 / 5 µs |
| BXT1 | min 1.4 × 10¹⁰ · typ 2.8 × 10¹⁰ | typ 2.0 × 10⁴ – 3.0 × 10⁴ | 6 / 12 µs |
| BXT2 (TO37) | min 1.6 × 10¹⁰ – 2.4 × 10¹⁰ | min 2.2 × 10⁴ – 1.2 × 10⁵ | 8 / 14 µs |
| BXT2S (TO8) | min 1.5 × 10¹⁰ – 2.0 × 10¹⁰ · typ up to 3.5 × 10¹⁰ (28T/38T — family’s highest) | min 1.65 × 10⁴ – 5.0 × 10⁴ · typ up to 7.5 × 10⁴ | 12 / 25 µs |
Specifications apply at a bias of 25 V/mm (cooled) or 35 V/mm (uncooled) with a 1 MΩ or 0.5 MΩ series load resistor; cooled specs at maximum cooling with a +25 °C heat sink. The datasheet publishes minimums for every part and typicals for selected parts — confirm your exact part number.
Matching D* to your optics: D* normalizes for area and bandwidth, so two detectors with the same D* but different element sizes deliver different signal levels. Larger elements (up to the 36 mm² BXT2S-68TE) capture more flux — match active area to your spot size and étendue rather than chasing D* alone. Response speed is set by the series, not the element size. Definitions in the glossary.
Typical Applications
- Fire, flame, gas & environmentalFlame detection, CO₂ and hydrocarbon gas measurement, emissions monitoring
- Industrial process controlProcess control systems, thermal imaging, moisture sensing
- Food analysisMoisture measurement via NIR/MWIR spectroscopy
- Medical diagnosticsMedical gas analysis
Deep dive on the flagship cooled series in the BXT2 two-stage cooled PbSe guide, or compare chemistries in the PbS vs PbSe selection guide (PbS covers 1–3 µm).
Datasheets & Downloads
The B Series datasheet covers all 13 standard part numbers: minimum/typical spec tables, spectral response curves, biasing diagrams, signal-to-noise plots, and TO5/TO8/TO37 package drawings. Start at the PbSe product category, get the full product catalog, or contact sales for the current revision. Complementary 1–3 µm coverage: PbS detectors.
Frequently Asked Questions
What is the difference between BXP, BXT1 and BXT2?
All three use the same PbSe sensing element. BXP is uncooled in a TO5 package; BXT1 adds a single-stage thermoelectric cooler (element at −25 °C); BXT2 adds a two-stage cooler (down to −45 °C on the BXT2S-28T/-38T) for the longest peak wavelengths and — on the BXT2S parts — the family’s highest detectivity. Choose by required D*, package, active area and budget.
What spectral range do Opto Diode PbSe detectors cover?
Roughly 1–5 µm in the mid-wave infrared. Uncooled BXP parts peak at 3.6–3.8 µm; cooling shifts the peak longer — 4.0–4.2 µm for BXT1 and 4.1–4.5 µm for BXT2 (the bandpass-filtered BXT2-17TF is specified at 4.3–4.7 µm).
Do PbSe detectors need cooling?
No — the uncooled BXP series operates at room temperature, one of PbSe’s practical advantages for compact MWIR instruments. Thermoelectric cooling (BXT1, BXT2) is chosen for higher detectivity, longer-wavelength response, or stability in fluctuating-temperature environments.
How do I get the full datasheet and exact specifications?
The datasheet lists per-part minimum/typical D* and responsivity, resistance ranges and time constants, plus package dimensions. Start from the PbSe product category page or contact us for the latest revision and custom configurations.
Can Opto Diode supply custom active areas, windows or filters?
Yes. Standard parts cover 1 to 36 mm² with flat sapphire, ARSi, 2.4 µm longpass and 4.7 µm bandpass options. Custom element sizes, packages, windows and cooling configurations are available — reach out with your optical and electrical requirements.
Specify Your PbSe Detector
Current datasheets, lead times, pricing, and custom BXP, BXT1 or BXT2 configurations — our applications engineers will match active area, cooling and window to your MWIR system.