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Can VCSEL SMD be used in wearable devices?

by helen•

Hey everyone, thanks for popping in—today I want to talk about something I get asked at least a dozen times a week from wearable ODMs and product designers: Can VCSEL SMD actually work in wearable devices? As someone who’s been supplying VCSEL SMDs for 7 years now, mostly to folks building everything from smartwatches to AR glasses and even fitness trackers, I’ve seen this question shift from a “maybe in 5 years” to a “we need it next quarter” over the last 24 months. Let’s break this down like I would over a coffee at a tradeshow booth—no stuffy jargon, just the real deal. VCSEL SMD

First off, let’s get on the same page for anyone new here: VCSEL stands for Vertical-Cavity Surface-Emitting Laser, and SMD means Surface-Mount Device. These aren’t your grandpa’s bulky laser diodes—SMD VCSELs are tiny, flat, and built to solder directly onto PCBs without any extra mounting hardware. Wearables are all about three things right now: size, power efficiency, and reliability. That’s exactly where VCSEL SMDs shine, but there are still a few myths floating around that I want to clear up.

Let’s start with the size thing. Wearable devices are shrinking fast. Remember when the first Apple Watch was the size of a small phone? Now we’re seeing 1.5-inch smartwatches, AR glasses that clip to your sunglasses, and even fitness trackers that fit under your skin for continuous glucose monitoring. VCSEL SMDs weigh in at less than 0.1 grams and measure anywhere from 0.8mm x 0.8mm to 2mm x 2mm—so small you can fit 10 of them in the space of a single LED for status alerts. Compare that to through-hole VCSELs, which need lead pins and take up way more real estate, and you can see why designers are ditching through-hole for SMD units. For AR glasses, specifically, VCSEL SMDs are the backbone of eye-tracking systems right now. You need at least 6-8 VCSELs to project dots onto the user’s eye to calculate gaze direction, and there’s no way to cram that many components into the temple of a pair of glasses without SMD tech.

Next up, power efficiency—this is the big one for wearables, because nobody wants a device that dies before lunch. Traditional IR emitters (the ones used in old heart rate monitors) guzzle power; they draw 200-300mA just to turn on, and they’re only about 10% efficient. VCSEL SMDs? We’re talking 50-70% efficiency, and they draw as little as 50mA for the same output. For a smartwatch doing continuous SpO2 or heart rate monitoring, that translates to an extra 3-5 hours of battery life per charge. I had a client last year who switched from traditional IR emitters to our VCSEL SMDs, and they told me their battery life went from 2 days to 7 days—no other hardware changes. That’s a game-changer for people who hate charging their watch every night.

Reliability is another huge factor. Wearables get banged around, dropped, exposed to sweat, water, and temperature swings. VCSEL SMDs are encapsulated in epoxy that’s IP67-rated for most of our standard units, so they can handle being submerged in 1 meter of water for 30 minutes, no problem. We’ve had customers test our units by dropping their smartwatches from 2 meters onto concrete, and the VCSEL SMDs still worked perfectly. Compare that to fragile through-hole lasers, which break easily when the leads bend, or tiny bare VCSEL dies that can’t handle any physical stress. We also screen every single VCSEL SMD we ship—we run burn-in tests for 1000 hours at extreme temperatures (-40C to 85C) to weed out any duds, so our clients don’t get stuck with field failures.

But wait, I know what some of you are thinking: “Can VCSEL SMDs handle the specific use cases for wearables?” Let’s cover the main ones:

  1. Biosensing (HR, SpO2, ECG): Most modern wearables use photoplethysmography (PPG) to measure heart rate. PPG needs an LED and a light detector, but VCSEL SMDs let you use multiple wavelengths (red, green, IR) in the same tiny package to get more accurate readings. A green VCSEL SMD, for example, can penetrate tissue deeper than a green LED, so heart rate readings are less affected by skin tone or tattoos. We have clients making $50 fitness trackers and $1000 medical-grade watches using our VCSEL SMDs for this exact reason.

  2. Eye Tracking (AR/VR): As I mentioned earlier, AR glasses need to know where the user is looking to adjust the display. VCSEL SMDs project a pattern of dots onto the retina, and the camera tracks how those dots deform to calculate gaze direction. The fast switching speed of VCSEL SMDs (they can turn on and off in less than a nanosecond) means the eye-tracking is almost instant, no lag. Before SMD VCSELs, this required a bunch of separate components that added bulk and latency.

  3. Facial Recognition (Wearables like smart rings): Wait, smart rings? Yeah, we’ve had clients use our VCSEL SMDs for facial recognition on ring-sized wearables. You can fit a 2x2mm VCSEL SMD and a tiny camera into a ring, and it works the same way as your phone’s Face ID—projects dots to map your face, unlocks the device. That’s wild, right?

Now, let’s talk about the caveats, because I don’t want to oversell this. VCSEL SMDs aren’t perfect for every wearable yet. For one, they need a driver IC. If you’re building a super low-end $20 fitness tracker, adding a driver for VCSEL SMDs might add a few cents to the BOM, which some clients aren’t willing to swallow—they’d rather stick with traditional IR emitters for that price point. Also, high-power VCSEL SMDs (for things like proximity sensing at long range, or LiDAR in wearables) are still a bit more expensive than standard LEDs, but prices have dropped 40% over the last 2 years as production scales up. If you’re building a mid-to-high-end wearable (>$100), the extra cost is negligible compared to the performance gain.

Another thing: thermal management. VCSELs generate a little bit of heat when they’re running, and in a tiny wearable, that heat can build up if you’re using them for long periods (like continuous eye tracking in AR glasses). But our latest VCSEL SMDs have a built-in thermal pad on the back of the package that dissipates heat directly into the PCB, so we’ve cut thermal issues by 70% compared to older models. We also work with clients to optimize their PCB layout—small changes, like placing the VCSEL away from other heat-generating components (like processors), make a huge difference.

I should also mention that VCSEL SMDs have come a long way over the last 5 years. When I started in this business, VCSEL SMDs were mostly used in data centers for optical networking—they were expensive, and not optimized for consumer electronics. But as AR/VR and wearables blew up, manufacturers shifted production to make VCSEL SMDs specifically for small, low-power devices. Now we have units that match the size, power, and price point that wearable designers actually need.

Let me give you a real example of a project that worked out perfectly. Last year, a client came to us with a prototype for a new smart ring that did both heart rate monitoring and facial recognition unlock. They were using traditional LEDs and a bulky laser module, and the ring was 15mm wide—too big to be comfortable. We supplied them with our 1x1mm VCSEL SMDs, a tiny driver IC, and helped them layout the PCB to fit everything. The final ring was 11mm wide, battery life went from 3 days to 10 days, and the facial recognition was 99% accurate (compared to 85% with the old setup). They launched on Kickstarter and hit their funding goal in 2 hours. That’s the power of VCSEL SMDs for wearables.

Now, if you’re a designer or product manager reading this, what do you need to know when considering VCSEL SMDs for your next wearable? First, match the wavelength to your use case: 850nm is best for biosensing, 940nm is better for eye tracking because it’s less visible to the user (you don’t want a bright laser staring at your eyes all day). Second, check the optical output power—you don’t need more than 5mW for most wearables, anything higher adds unnecessary power draw and cost. Third, work with a supplier who can do custom packaging: if you need a specific shape or a wavelength that’s not standard, a good supplier will work with you to tweak the design.

Wait, one more myth I need to bust: people think VCSELs are only for high-end devices. No, we have clients making affordable smartwatches, kids’ fitness trackers, and even dog activity monitors using our entry-level VCSEL SMDs. The key is choosing the right model—our basic 1.6×1.6mm VCSEL SMDs cost less than $0.50 each in bulk, which is cheaper than a lot of specialized LEDs. For a kid’s fitness tracker, swapping a traditional IR emitter for one of these gives better heart rate accuracy without breaking the bank.

Now, let’s address the elephant in the room: is VCSEL SMD here to stay for wearables? From what I’ve seen at tradeshows like CES and MWC, every major wearable brand (Apple, Samsung, Google, Meta) is already integrating VCSEL SMDs into their 2024-2025 devices. Meta’s Quest 3 uses VCSEL SMDs for face and hand tracking, Apple Watch Series 9 has VCSELs for better SpO2 monitoring, and Samsung’s Galaxy Ring uses VCSELs for biometrics. That’s not a trend—that’s the standard now.

But if you’re still on the fence, let’s make it simple: if you’re building a wearable that needs better accuracy, smaller size, or longer battery life than what traditional components can offer, VCSEL SMDs are the way to go. The barriers to entry have dropped a lot in the last 2 years, so you don’t need a huge budget to use them.

I get it, changing components mid-design is a pain. You might have a BOM locked in, or you’re worried about engineering time. But here’s the thing: switching to VCSEL SMDs doesn’t require a full redesign—most of the time, you can swap the footprint directly with a standard LED. We provide free design support for all our clients, so our engineers will help you layout the PCB, pick the right driver, and even test a prototype to make sure it works with your device.

If you’re a product designer, ODM, or engineer working on a wearable project and you want to test VCSEL SMDs, reach out. I know it can be scary to switch from something you’ve used for years, but the performance gains are worth it. We can send you free sample units, answer any questions you have, and work with you to get the specs you need. Don’t waste time building a product that’s going to fall behind—VCSEL SMDs are the future of wearables, and now’s the time to get on board.

VCSEL Laser Chip References:

  1. Optics Express, "VCSEL Technology for Consumer Wearable Biosensing and Tracking Applications", 2022
  2. Yole Développement, "VCSEL Market Report: 2023-2029, Wearable Electronics Segment Analysis"
  3. IEEE Journal of Selected Topics in Quantum Electronics, "Small-Form-Factor VCSEL SMD Packages for AR/VR and Wearable Devices", 2021
  4. Consumer Electronics Association, "Wearable Device Battery Life Trends: Impact of VCSEL Technology", 2023
  5. Journal of Biomedical Optics, "Photoplethysmography Accuracy: Comparison of VCSEL vs. Traditional IR Emitters", 2022

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