What Is a VCSEL at 795/895 nm? A Manufacturer’s Guide for Atomic & Quantum Sensing
What is a VCSEL?
A VCSEL is a semiconductor laser that emits light straight out of the chip surface rather than from the edge. This geometry enables on-wafer testing, easy array formation, and compact packaging. Modern VCSELs offer excellent wavelength stability over temperature and can pair well with narrow IR bandpass filters to clean up background noise at the detector.
Why 795 nm and 895 nm?
795 nm: Rubidium (Rb) D1 transition. Ideal for optical pumping and probing in Rb vapor cells within compact clocks and magnetometers.
~894.6–895 nm: Cesium (Cs) D1 transition. A go-to band for micro-clocks and related timing modules.
Tuning a VCSEL to either D1 line makes it easier to lock the laser to atomic absorption features while keeping the optical head small and power-efficient.
Inside a VCSEL: Cavity & DBRs—Why It Matters
A VCSEL uses two high-reflectivity DBR mirrors that form a short vertical resonator around quantum wells. This architecture supports:
Single-mode operation with low divergence (clean coupling through tiny windows),
Low threshold current (friendly to battery-powered systems),
Tight wavelength control via temperature and drive current—exactly what you need near an atomic reference.
Key Advantages for Atomic & Quantum Builds
Surface emission → wafer-level testing and better scalability.
High efficiency and low power draw with symmetric, low-divergence beams—great for tiny optics.
Controllable polarization & single transverse mode for repeatable optical pumping.
Exceptional wavelength stability vs. temperature for stable locks.
Applications That “Love” 795/895 nm
Chip-Scale Atomic Clocks (CSACs): Slender optics, tight thermal budgets, long-term stability.
SERF Magnetometers: Push toward femto-tesla sensitivity; any stray magnetic material or large current loop can swamp the signal.
Bio/Med & Industrial Sensors: Where narrowband, stable IR sources are preferred.
Packaging for Quantum Labs: Why “Non-Magnetic” Isn’t Optional
Non-magnetic packaging prevents bias fields and hysteresis that would otherwise corrupt low-field measurements. Using ceramic headers and non-magnetic lids (plus careful current routing) keeps the field near the vapor cell quiet—so you can place the light source within millimeters of the cell. Commercial reports show SNR gains when replacing steel-can devices with non-magnetic builds in quantum sensing.
Materials & layout choices that help:
Headers: ceramics; housings: titanium or aluminum
Finishes: gold-based; fasteners: non-magnetic
Adhesives/solders: no magnetic fillers
Heaters/sensors: integrated with tight loop area; minimize return paths near the cell
Windows & Coatings at 795/895 nm
Fused silica or sapphire windows with AR coatings centered at one or both D1 lines.
Wedge or angled lids reduce back-reflections and etalons that would disturb the cavity or your detector baseline.
Hard coats help stability across humidity and handling.
Manufacturer’s Note: Configurations We Ship Frequently
We manufacture VCSELs end-to-end—from epitaxial wafer to finished package—and supply 1 mW class emitters at 795 nm and 895 nm in customizable packages including SMD, TO-style, and non-magnetic options suited to magnetometer and micro-clock designs. Our single-mode lineup spans roughly 750–900 nm, with an emphasis on wavelength and polarization stability over a wide operating temperature range.
We also support on-wafer probing and binning (wavelength/threshold/slope efficiency) before singulation to hit tight wavelength buckets at 25 °C and streamline production.
High-temperature capability: Our VCSELs are rated for ambient operation up to 150 °C (application dependent).
Power, Beam, and Polarization for Vapor Cells
Power: ~1 mW single-mode is a practical starting point for most Rb/Cs cells; it leaves margin for filters/fibers and minimizes heat.
Beam quality: M² ≈ 1 and low divergence simplify alignment through micro-optics.
Polarization: Stable linear polarization shortens bring-up and improves repeatability in optical pumping.
Tuning & Locking—Without the Drama
Temperature/current tuning: Expect a consistent wavelength shift vs. °C and mA, enabling small, infrequent corrections to hold line center.
Compact locks: Many teams pass a beam through a miniature reference cell and derive an error signal from D1 absorption features; a low-heat VCSEL keeps the whole head pocket-sized.
Practical Driver & Heater Tips (Low-Field Friendly)
Keep current loops tight; twist pairs and bring returns close to sources.
Avoid nickel-plated metals near the cell; place sensors near the junction for fast thermal feedback with minimal heater current.
Flexible circuits that co-locate the laser, heater, and sensor can markedly reduce stray fields.
From Epitaxy to Packaged Part: Our Flow
Wafer growth & patterning → oxide/current confinement built-in.
On-wafer screening → early binning by wavelength, threshold, slope for predictable builds.
Assembly & sealing → your window type/coating, followed by burn-in and stability checks.
Magnetic cleanliness verified on non-magnetic part sets.
How to Specify Your Order (Checklist)
Optical
Target wavelength: 795 nm or ~895 nm; allowed offset at 25 °C
Output at operating point (mA & °C)
Beam: single-mode, far-field divergence requirement
Polarization: linear (preset or external control)
Package & Window
Non-magnetic vs magnetic (SMD or TO-style)
Window: fused silica or sapphire; AR@795/895 nm; wedge or flat; lid angle if needed
Space constraints, pin map, connector style
Thermal/EMC
Heater control strategy & set-points
Sensor type/placement (e.g., thermistor/RTD)
Cable routing/grounding rules; loop-area limits
Two Reference Build Recipes
Rb Cell Magnetometer Head (1 mW, non-magnetic)
Laser: 795 nm single-mode VCSEL, ~1 mW
Package: Non-magnetic ceramic header + titanium cap
Window: Fused silica, AR@795 nm, ~2° wedge
Polarization: Linear preset at lid
Thermal: Integrated heater + RTD on flex
Note: Laser placed ~3–5 mm from the vapor cell; routing keeps loop area minimal.
Cs Micro-Clock Lamp Source
Laser: ~895 nm VCSEL, ~1 mW
Package: SMD or compact TO; window AR@895 nm
Polarization: Linear
Thermal: Board-level heater; temp set near D1 line center
Note: Low-ripple driver below instrument noise floor.
FAQs
Q1: What is a VCSEL and why is it preferred over edge-emitters here?
A VCSEL emits from the wafer surface, allowing wafer-level screening, compact arrays, and stable wavelength-vs-temperature behavior—good news for small, thermally constrained instruments.
Q2: Why pick 795/895 nm instead of 780/852 nm?
Because 795 nm (Rb D1) and ~895 nm (Cs D1) directly address the D1 transitions, many compact devices find these lines easier to lock and friendlier to small, warm vapor cells.
Q3: Do you offer both magnetic and non-magnetic versions with the same optics?
Yes—teams often validate with a cost-optimized TO build and later migrate to a non-magnetic family with the same optical spec.
Q4: Do you support windows/coatings tuned to both 795 and 895 nm?
Yes—dual-band AR, wedges, and angled lids are available to suppress reflections at both lines.
Q5: What output power should I begin with?
Start around 1 mW (single-mode) for most Rb/Cs cells; it leaves margin for filters/fibers while keeping heat and drive power modest.
Why Work With Us (as a Manufacturer)
Custom epitaxy & device structures for GaAs-based VCSELs, plus deep chip-process know-how (ICP etch, wet oxidation, BCB).
Experience delivering 795/895 nm, ~1 mW parts in SMD, TO-46, and non-magnetic packages for magnetometer designs worldwide.
Single-mode coverage ~750–900 nm with tight wavelength & polarization stability, and options to integrate thermistors/TECs on-package.
Rated for high ambient temperatures (up to 150 °C) where applications require it.
Gentle CTA
If you need a 795 nm or ~895 nm VCSEL for an atomic clock or SERF magnetometer—and you want the same optical spec available in both non-magnetic and TO/SMD formats—reach out with your checklist. We’ll bin to your wavelength, set polarization at the lid if you like, and help you lock quickly on day one.