488 nm and 473 nm sit fifteen nanometres apart and both read as blue. But unlike most wavelength comparisons, this one is not really about the fifteen nanometres. It is about two fundamentally different laser technologies that happen to land near each other on the spectrum — a semiconductor diode on one side, a frequency-doubled solid-state crystal on the other.
That means the choice carries consequences well beyond excitation efficiency: beam quality, available power, polarisation, and — the detail most often missed — whether you can modulate the beam at all.
Two Different Machines
488 nm is a direct diode. Light is emitted straight from a semiconductor junction, with output controlled by drive current. No conversion stage, no crystal. This makes high power straightforward — our standard and low-noise models reach 1500 mW — and it makes fast modulation intrinsic, because varying the current varies the light.
473 nm is DPSS. It is the second harmonic of the 946 nm Nd:YAG transition, a quasi-three-level line that is considerably weaker than the 1064 nm transition most DPSS lasers exploit. Getting it to oscillate at all requires careful cavity design, and the achievable power is correspondingly modest — 300 mW at the top of our range. What you get in exchange is the thing DPSS does best: a clean TEM₀₀ beam straight out of the cavity.
If the general trade-offs between these two technologies are new to you, our guide on diode laser vs. DPSS laser covers them in full. Here we focus on what they mean at these two specific wavelengths.
The Fluorophore Case for 488 nm
For fluorescence work, 488 nm is not merely the more popular choice — it is the correct one for most of the blue-excited palette, and the margin is not close.
EGFP peaks at 488 nm. Not near it — at it. Enhanced GFP, the variant in essentially universal use, has its excitation maximum precisely where the laser sits. Wild-type GFP is a different story, with a major peak near 395 nm and a secondary near 475 nm, but almost nobody images wild-type GFP any more.
FITC and Alexa Fluor 488 peak around 495 nm — just past 488 nm, on the far side from 473 nm. Both are excited efficiently at 488 nm and noticeably less so at 473 nm, because 473 nm sits further down the rising flank of the spectrum.
| Fluorophore | Excitation peak | Better choice |
|---|---|---|
| CFP / mCerulean | ~433–445 nm | 473 nm — but 445 nm is better still |
| ChR2 (channelrhodopsin-2) | ~470 nm | 473 nm |
| PerCP | ~482 nm | Either — both close |
| EGFP | ~488 nm | 488 nm — exact match |
| FITC | ~495 nm | 488 nm |
| Alexa Fluor 488 | ~495 nm | 488 nm |
| YFP / Venus | ~514 nm | 488 nm — or 532 nm |
| PE (secondary peak) | ~496 nm | 488 nm — or 561 nm at its true peak |
The asymmetry is the point. Nearly every workhorse fluorophore in this region peaks at 488 nm or above, which puts 473 nm on the wrong side of all of them. There is no commonly used dye sitting at 473 nm waiting to be matched. For flow cytometry in particular — where 488 nm has been the primary blue line for decades and where PE, FITC, PerCP, and GFP all share it — this settles the question. Our flow cytometry laser guide covers how the blue line fits alongside the rest of a panel.
Where 473 nm Earns Its Place
None of which makes 473 nm a lesser laser. It wins on three counts, and each is decisive in the right context.
Channelrhodopsin-2
ChR2 has its action-spectrum peak near 470 nm, making 473 nm very nearly a perfect match. For optogenetics this is the wavelength of record, and it is why 473 nm appears in far more neuroscience rigs than its fluorescence footprint would suggest. (More on opsin matching in what laser you need for optogenetics.)
Beam quality, at every tier
This is 473 nm's structural advantage. Every 473 nm variant — standard, low noise, and Pro — delivers a TEM₀₀ beam at M² < 1.2 with a sub-millimetre diameter and > 100:1 polarisation.
The 488 nm diode reaches comparable beam quality only in its Pro variant (DLCZ-488, M² < 1.1), and that variant tops out at 30 mW. The standard and low-noise 488 nm models are multimode with a 3 × 3 mm beam and > 50:1 polarisation. So if you need a clean single-mode blue beam at 100 mW or more — for holography, interferometry, or efficient single-mode fibre coupling — 473 nm is the only one of the two that offers it.
Polarisation
473 nm specifies > 100:1 as standard across the range. The 488 nm diode is > 50:1 with 100:1 available as an option. For polarisation-sensitive measurements, anisotropy work, or structured-illumination patterning, that difference is worth checking.
The Modulation Catch
Here is the detail that catches people out, and it cuts against the wavelength logic in a way worth understanding before you order.
On our 488 nm diode, TTL and analog modulation from DC to 30 kHz is standard on every variant. It comes with the laser because that is simply how a diode works.
On our 473 nm DPSS, modulation is available as an option. This is inherent to the architecture: the pump, gain crystal, and doubling crystal form a thermally coupled chain that does not respond instantly to changes in pump current.
Now put that against optogenetics. ChR2 protocols are built on pulse trains — millisecond pulses at 20–40 Hz, synchronised to electrophysiology. So the wavelength that best matches ChR2 is also the one whose modulation needs specifying up front. And because the ChR2 action spectrum is broad, 488 nm still drives it well despite sitting 18 nm off peak. That is precisely why our optogenetics application page lists both wavelengths for ChR2 rather than just the closer one.
The practical upshot: if you are pulsing ChR2 hard, weigh a 488 nm diode with native fast modulation against a 473 nm DPSS specified with the modulation option. Peak match is not the only variable.
Specification Comparison
| Parameter | 488 nm (Diode) | 473 nm (DPSS) |
|---|---|---|
| Source | Direct semiconductor emission | SHG of 946 nm Nd:YAG |
| Max power | 1500 mW | 300 mW |
| Beam mode (Standard / Low Noise) | Multimode | TEM₀₀, M² < 1.2 |
| Beam mode (Pro) | TEM₀₀, M² < 1.1 — up to 30 mW | TEM₀₀, M² < 1.2 — up to 100 mW |
| Beam diameter | < 3 × 3 mm (< 1 mm on Pro) | < 1 mm |
| Polarisation | > 50:1 (100:1 optional) | > 100:1 |
| Modulation | DC – 30 kHz, TTL/Analog — standard | DC – 30 kHz, TTL/Analog — optional |
| Power stability | < 1% RMS | < 1% RMS |
| Warm-up | < 5 min | < 5 min |
| Head dimensions | 143.5 × 73 × 46.2 mm | 142.5 × 60 × 50 mm |
How to Decide
- Imaging GFP, FITC, Alexa Fluor 488, or running flow cytometry? 488 nm. This covers the large majority of use cases and is not a close call.
- Driving ChR2? 473 nm matches the peak — but specify the modulation option, or consider a 488 nm diode if your protocol depends on fast pulse trains.
- Need TEM₀₀ above 30 mW in the blue? 473 nm. The 488 nm diode only reaches that beam quality in its 30 mW Pro variant.
- Need serious power — high-throughput screening, deep samples, lossy optics? 488 nm, by a factor of five.
- Polarisation-critical measurement? 473 nm gives you > 100:1 as standard.
A useful summary: choose 488 nm for fluorescence, and 473 nm for beam quality and ChR2. Most laboratories that own both are using them for genuinely different experiments rather than treating them as alternatives.
Aimpico 488 nm and 473 nm Lasers
The 488 nm family comprises DMCE-488 (standard) and DMCZ-488 (low noise) from 100 to 1500 mW multimode, plus DLCZ-488 (Pro) delivering TEM₀₀ at M² < 1.1 up to 30 mW with > 100:1 polarisation. All three carry TTL and analog modulation from DC to 30 kHz as standard.
The 473 nm family runs SLCE-473 (50–300 mW), SLCZ-473 (20–300 mW, low noise), and SLCP-473 (20–100 mW, Pro) — all TEM₀₀ at M² < 1.2 with < 1 mm beam diameter and > 100:1 polarisation, in a 142.5 × 60 × 50 mm head shared across all three tiers.
Tell us your fluorophores or your opsin, along with the power you need at the sample and whether you are pulsing, and we will point you at the right line.
Choosing between 488 nm and 473 nm for your system?