What Is VCSEL at 795 nm? Why Atomic & Magnetometer Systems Prefer Non-Magnetic Packages

Short answer to “what is VCSEL”: a Vertical-Cavity Surface-Emitting Laser is a semiconductor laser that emits light vertically from the chip surface. This geometry enables wafer-level testing, tight wavelength control, and stable performance across temperature—ideal traits for precision sensing.

TL;DR for Atomic & Quantum Engineers

  • 795 nm VCSELs align with the Rb D1 transition, making them a go-to source for compact atomic clocks and optically pumped magnetometers (OPMs).

  • Packaging matters: even tiny ferromagnetic parts can bias your field. Non-magnetic headers/lids and Ni-free finishes cut field artifacts at the cell.

  • Ace Photonics supplies 790/795 nm and 890/895 nm VCSELs in bare die, SMD, TO-46, and custom non-magnetic packages, plus 760/763 nm options—covering common alkali lines and related sensing needs.

What Is a VCSEL?

A VCSEL is built like a tiny optical resonator “stack”: DBR mirrors above and below a thin gain region. When current flows, light resonates between the mirrors and exits the top as a clean, round beam. Because emission is from the wafer surface, devices can be probed before dicing, and the cavity design supports excellent wavelength stability vs. temperature—key for keeping on-resonance with narrow atomic lines.

Why 795 nm Is the Sweet Spot for Rubidium Devices

The Rb D1 line near 795 nm is ubiquitous in chip-scale atomic clocks and OPMs. When the laser is single-mode with narrow linewidth and stable polarization, optical pumping is cleaner and readout noise lower—improving frequency stability (clocks) and sensitivity (magnetometers). Ace Photonics builds 795 nm parts specifically for these use cases, alongside 895 nm (Cs D1) for alternative architectures.

Ace Photonics 795 nm VCSEL in non-magnetic ceramic package with quartz window, single-mode beam for rubidium D1 atomic clock and OPM applications.

Product-Aligned Wavelengths & Power Classes

Ace Photonics’ portfolio covers the wavelengths atomic teams ask for most:

  • 790/795 nm (Rb D1), available at 0.1 mW, 1 mW, and 1.8 mW

  • 890/895 nm (Cs D1), available at 0.1 mW, 1 mW, and 1.8 mW

  • 760/763 nm (auxiliary atomic/diagnostic use), 0.3 mW
    Each can be delivered as bare die, TO, SMD, or customized non-magnetic packages to match your mechanical and field budget.

Ace’s single-mode series spans roughly 750–900 nm, and can be integrated with on-package thermistors/TEC for tight thermal control—useful when you’re locking to atomic lines under varying ambient conditions.

Why Non-Magnetic VCSEL Packaging Is Often Make-or-Break

In SERF/zero-field OPMs and other ultra-low-field sensors, ferromagnetic metals in a standard can can add local bias and drift. Non-magnetic packages (ceramic headers, specialty lids, Ni-free plating stacks) maintain a field-silent neighborhood at millimeter distances from the vapor cell. Reported results in quantum sensing include order-of-magnitude SNR improvements when substituting non-magnetic for conventional cans.

Where non-magnetic VCSELs help:

  • SERF OPMs: reduce package-induced bias so the cell “sees” the world, not the housing.

  • MRI-compatible optics: avoid imaging artifacts and interaction with strong fields.

  • Atomic clocks, gyros, precision metrology: preserve the purity of your measurement baseline.

Packaging Options for Real Systems

Ace Photonics offers a broad packaging palette so you can trade size, thermals, and integration effort against magnetic cleanliness:

  • TO-Can (TO-46), Ceramic, Butterfly, SMD/PLCC, and Custom options.

  • Non-magnetic builds with ceramic headers, Ni-free gold finishes, and compatible solders/epoxies.

Because VCSELs are surface emitters, they map well to SMD/PLCC modules used across electronics—handy for compact, high-volume assemblies.

Specs That Matter for Atomic/OPM Work

When you evaluate “what is VCSEL at 795 nm good for,” focus on practical, atomic-relevant metrics:

  1. Wavelength placement & tuning

    • Nominal 790/795 nm (Rb D1) or 890/895 nm (Cs D1) with controlled tuning vs. current/temperature for precise line alignment.

  2. Linewidth & SMSR

    • Single-mode emission, narrow linewidth (MHz-class typical of atomic builds), high side-mode suppression for clean pumping.

  3. Polarization stability

    • Stable linear polarization helps maintain state preparation quality and lowers readout noise.

  4. Beam quality

    • Round, near-Gaussian output simplifies coupling into tiny vapor cells.

  5. Thermal robustness

    • VCSELs support excellent wavelength stability vs. temperature, and Ace’s devices are rated to high ambient operating temperatures (up to 150 °C) for rugged conditions.

  6. Power & noise

    • ~0.1–1.8 mW classes cover most chip-scale cells without overheating; low RIN/flicker set a lower sensor noise floor.

  7. Integration readiness

    • Wafer-level testability improves device screening and lot-to-lot uniformity before packaging.

Application Snapshots

Rb Vapor-Cell Clock at 795 nm

A single-mode 795 nm VCSEL couples into a millimeter-scale Rb cell. With the line pinned and polarization stable, the servo sees a clean discriminator. Non-magnetic packaging keeps field perturbations negligible at the cell.

Zero-Field OPM

In SERF operation, even micro-tesla artifacts from a magnetic lid can raise the noise floor. Ceramic headers, Ni-free Au finishes, and compatible solders keep local fields flat—unlocking the sensitivity you modeled.

Why Ace Photonics for 795/895 nm VCSELs

  • Process depth: GaAs VCSEL R&D, ICP etch, wet oxidation, BCB—tuned for high-reliability chips.

  • Rigorous device screening: wafer-level probing and inspection support consistent performance, with packaging flexibility from bare die to non-magnetic TO/SMD.

  • Quantum-ready options: emission at 795 nm/895 nm, cavity/linewidth engineering, and non-magnetic headers/lids to keep your field quiet.

FAQs (Search-Friendly)

Q1. What is VCSEL in simple terms?
A compact laser that emits vertically from the chip surface—efficient, easy to align, and proven in precision sensing.

Q2. Why 795 nm for rubidium gear?
It targets the Rb D1 line, enabling clean optical pumping and stable readout in clocks and OPMs—assuming single-mode, narrow linewidth, and stable polarization. (Ace provides dedicated 790/795 nm parts.)

Q3. Why non-magnetic packaging in magnetometers?
Ferromagnetic metals near the vapor cell bias the local field. Non-magnetic headers/lids and Ni-free plating minimize that bias; teams report large SNR gains vs. standard cans.

Q4. What packages are available?
TO-Can (TO-46), Ceramic, Butterfly, SMD/PLCC, and custom builds—including non-magnetic variants.

Q5. What power do small vapor cells need?
0.1–1 mW covers many compact cells; Ace also offers 1.8 mW for higher margin or lossier optics.