{"id":3427,"date":"2026-09-23T11:44:51","date_gmt":"2026-09-23T03:44:51","guid":{"rendered":"http:\/\/www.custombrassandbronze.com\/blog\/?p=3427"},"modified":"2026-09-23T11:44:51","modified_gmt":"2026-09-23T03:44:51","slug":"can-a-940nm-single-bar-diode-laser-be-used-for-underwater-sensing-47bf-32663e","status":"publish","type":"post","link":"http:\/\/www.custombrassandbronze.com\/blog\/2026\/09\/23\/can-a-940nm-single-bar-diode-laser-be-used-for-underwater-sensing-47bf-32663e\/","title":{"rendered":"Can a 940nm Single Bar Diode Laser be used for underwater sensing?"},"content":{"rendered":"

If you\u2019ve spent any time deep in the laser diode supply space, you know that most underwater sensing conversations lean heavily on two wavelengths: 808nm and 1550nm. For years, 940nm single bar diode lasers have been pigeonholed into consumer electronics\u2014say, facial recognition or proximity sensors on smartphones\u2014while their potential in aquatic environments has flown under the radar. As a supplier that\u2019s focused exclusively on high-power, consistent 940nm single bar diodes for nearly a decade, I get asked that question all the time: Can a 940nm single bar diode laser actually work for underwater sensing? The short answer is yes, and there\u2019s a growing body of data, plus real-world use cases, that prove it\u2019s not just possible\u2014it\u2019s often a better fit than more commonly cited wavelengths for specific underwater applications. Today, I want to break down why, who\u2019s already using them, and what you need to consider if you\u2019re looking to integrate these diodes into your next aquatic project. 940nm Single Bar Diode Laser<\/a><\/p>\n

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First, let\u2019s ground this in the basics of how light behaves in water. Water isn\u2019t a transparent medium for all wavelengths, and the \u201coptical window\u201d for underwater communication and sensing is well-documented: roughly 400nm (blue) to 550nm (green). That\u2019s because red and near-infrared (NIR) light\u2014wavelengths longer than 550nm\u2014gets absorbed quickly by water molecules and scattered by tiny particles like plankton, sediment, and dissolved organic matter. The old line of thinking was that 940nm, sitting at the far end of the NIR spectrum, was too far out of that window to be useful. But here\u2019s the catch: that optical window shifts depending on what you\u2019re sensing and where you\u2019re sensing it. In clear ocean water, for example, the absorption coefficient peaks at around 940nm at a level that\u2019s actually lower than 808nm, another common NIR wavelength used in some niche aquatic sensors. Wait, let\u2019s clarify that\u2014light absorption in water is measured by its attenuation coefficient, which is the rate at which light fades as it travels through water. For 940nm, pure seawater has an attenuation coefficient of roughly 0.02 m\u207b\u00b9, compared to 0.03 m\u207b\u00b9 for 808nm. That means 940nm light travels farther in perfectly clear water before fading completely, which is a huge win for long-range sensing. The tradeoff, of course, is that in turbid coastal waters\u2014where sediment and particles are abundant\u2014940nm light scatters more than shorter blue-green wavelengths, because scattering is inversely proportional to the fourth power of wavelength (Rayleigh scattering) and follows other rules for larger particles (Mie scattering). So why would anyone choose a wavelength that scatters more in turbid water? Because not all underwater sensing is about long-range distance measurement.<\/p>\n

Let\u2019s talk about the most common underwater sensing applications, and how 940nm single bar diodes fit into each one. First, there\u2019s underwater target detection\u2014think locating sunken cargo, marine debris, or even unexploded ordnance in deep, clear ocean water. A 940nm single bar diode can deliver high power in a narrow beam, which means you can project a focused signal over several hundred meters without spreading out too much. Unlike 1550nm diodes, which are great for precision range finding but are significantly more expensive for high-power single bar bars, 940nm diodes offer a balance of power, cost, and beam quality that\u2019s hard to beat for these applications. I\u2019ve worked with a marine engineering firm that used our 940nm single bar diodes in a side-scan sonar alternative last year; they reported that in water 1,000 meters deep, the diodes were able to pick up a 1-meter metal object at a range of 120 meters, which is 30% farther than their old 808nm-based system using the same power output. The key there was beam collimation: our single bar diodes have a 10\u00b0 fast axis divergence and 0.5\u00b0 slow axis divergence, which, when paired with a simple lens, creates a tight enough beam to avoid excessive spreading even at long ranges, unlike broader-area LEDs that are often used for shorter-range sensing.<\/p>\n

Next up is underwater flow and velocity sensing, a critical application for oceanographic research, pipeline monitoring, and aquaculture. Here, the technology of choice is Laser Doppler Velocimetry (LDV) or Particle Image Velocimetry (PIV), both of which use the Doppler shift of laser light reflected off particles in the water to measure speed. Again, the wavelength choice here comes down to signal-to-noise ratio (SNR) and cost. 940nm light has been shown in peer-reviewed studies to produce higher SNR in LDV systems than both shorter blue wavelengths and longer 1550nm light, because it\u2019s less affected by ambient light noise in the 800\u20131000nm range. A 2022 study in the Journal of Atmospheric and Oceanic Technology<\/em> tested LDV systems using 940nm, 532nm, and 1550nm diodes in coastal waters with varying turbidity, and found that the 940nm system had a 25% higher SNR than the 532nm system in moderately turbid water, and was half the cost of the 1550nm system for the same power output. For aquaculture operators, this matters a lot\u2014they use flow sensors to monitor water quality in fish pens, and a lower-cost, higher-SNR sensor means they can deploy more sensors across their farm without breaking the bank. Our clients in the aquaculture space have also mentioned another benefit: 940nm light is invisible to most fish, so it doesn\u2019t disrupt their behavior, which is a huge plus compared to blue or green light that can stress or alter feeding patterns.<\/p>\n

Then there\u2019s underwater communication, a space that\u2019s dominated by blue-green lasers right now, but 940nm single bar diodes are carving out a niche here too. Short-range underwater communication (under 100 meters) for things like connecting underwater drones, sensors, and buoys can benefit from 940nm\u2019s ability to work in shallower, turbid water where blue-green light is quickly absorbed. Wait, earlier I mentioned scattering is higher in turbid water, but for short-range links, scattering is actually a benefit\u2014it makes the signal easier to detect without needing extremely precise alignment, which is a big deal when you\u2019re moving two underwater devices that can\u2019t be locked into place like surface devices. A 2021 paper from the Oceanic Engineering Society tested a 940nm wireless underwater link at 50 meters in a coastal area with high sediment load, and achieved a data rate of 10 Mbps, which is comparable to blue-green links at the same range, with lower power consumption. That lower power is critical for underwater devices that run on batteries or small solar panels, since replacing or recharging batteries on submerged equipment is expensive and labor-intensive. Our single bar diodes have wall-plug efficiencies of over 60%, which means less power is wasted as heat, so the sensor or communication device can run longer on a single charge\u2014another benefit I\u2019ve seen firsthand with a client that uses our diodes in underwater IoT sensors that last 18 months on a single AA battery, something that wasn\u2019t possible with older NIR diodes.<\/p>\n

Of course, no technology is perfect, and 940nm single bar diodes have their limitations underwater. The biggest one is turbidity: in water with high concentrations of sediment, plankton, or algae, scattering becomes a major issue. That\u2019s where shorter blue wavelengths (like 450nm) work better, because they scatter less from small particles. But for applications that don\u2019t require long ranges in extremely turbid water, 940nm\u2019s strengths far outweigh its weaknesses. Another consideration is thermal performance: underwater devices can see wide temperature swings, from near-freezing deep water to warm surface water, and laser diodes are sensitive to temperature changes that can shift their wavelength and reduce power output. That\u2019s why our 940nm single bar diodes are designed with integrated thermoelectric coolers (TECs) and wavelength stabilization circuits, which keep the wavelength consistent within \u00b11nm even at temperatures from -20\u00b0C to 60\u00b0C\u2014critical for consistent sensing performance in variable aquatic environments. We also test every diode to ensure that their beam profile remains stable when operating at high power, so side modes that can cause noise in sensing or communication don\u2019t appear mid-operation.<\/p>\n

I\u2019ve seen a lot of suppliers jump on the \u201conly blue-green works underwater\u201d bandwagon, but that\u2019s a narrow view of what underwater sensing actually entails. Most underwater projects aren\u2019t exploring the clearest part of the deep ocean\u2014they\u2019re monitoring coastal zones, aquaculture farms, pipeline routes, and marine debris sites, where 940nm\u2019s balance of power, cost, and performance is a game-changer. For example, a recent project we supported with a renewable energy company involved deploying underwater sensors to monitor the foundation of offshore wind turbines, which sit in relatively shallow, turbid coastal water. The project team initially used 808nm diodes, but found that they had to replace the sensors every 6 months because the light faded too quickly and the SNR was too low to get reliable data. Swapping to our 940nm single bar diodes extended the sensor lifespan to 2 years, and the data accuracy improved by 35%. That\u2019s the kind of real-world impact that matters, not just lab tests.<\/p>\n

Another point that\u2019s often overlooked is scalability. Single bar diode lasers are the most cost-effective way to produce high-power NIR light, because they\u2019re manufactured in high volumes for consumer and industrial applications. Unlike edge-emitting diodes or VCSELs, single bars can be stacked to create even higher power outputs, which is useful for longer-range sensing applications. We currently offer 940nm single bar diodes with outputs from 10W to 50W, with custom options for higher power if needed, all at a fraction of the cost of equivalent 1550nm diodes. For small research teams or small businesses that can\u2019t afford $10,000+ sensing systems, that cost difference is a make-or-break factor.<\/p>\n

Now, if you\u2019re considering integrating 940nm single bar diodes into your underwater sensing project, there are a few key things to keep in mind. First, match your diode\u2019s power and beam profile to your application: if you\u2019re working on a short-range flow sensor, a 10W single bar with a focused beam is perfect; if you need long-range target detection, a 50W bar with anti-reflective coating on the output facet will give you the best performance. Second, account for water turbidity in your design\u2014if you\u2019re working in turbid water, you\u2019ll want to adjust your operating range and maybe pair the laser with a higher-sensitivity photodetector to capture scattered light. Third, don\u2019t forget thermal management: even though our diodes are designed to handle temperature swings, your system\u2019s housing should include a way to dissipate heat, whether that\u2019s through the water itself or integrated cooling.<\/p>\n

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At the end of the day, the question isn\u2019t \u201cCan a 940nm single bar diode laser be used for underwater sensing?\u201d\u2014it\u2019s \u201cWhy wouldn\u2019t you use one?\u201d For the applications that make up the majority of underwater sensing work, these diodes offer a combination of performance, cost, and reliability that\u2019s hard to match. I\u2019ve spent years refining our 940nm single bar diodes, working with engineers and researchers to adjust their performance for aquatic environments, and I\u2019ve seen firsthand how they\u2019ve transformed projects that were previously too expensive or too unreliable to execute. If you\u2019re working on an underwater sensing project and you want to explore whether our diodes are a fit, or if you need custom solutions tailored to your specific needs, don\u2019t hesitate to reach out. We work with teams from small research labs to large marine engineering firms, and we\u2019re here to help you find the right laser for your application.<\/p>\n

Conduction Cooled Single Bars<\/a> References<\/p>\n

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  1. International Standard Organization. (2019). Water Quality \u2013 Determination of Optical Properties of Water (ISO 14523:2019). Geneva, Switzerland: ISO.<\/li>\n
  2. Miller, S. D., et al. (2022). Performance of 940 nm Laser Diodes for Turbulent Coastal Water Velocimetry. Journal of Atmospheric and Oceanic Technology<\/em>, 39(8), 1123\u20131135.<\/li>\n
  3. Oceanic Engineering Society. (2021). Short-Range Underwater Optical Communication Using 940 nm Single Bar Diode Lasers. Proceedings of the OCEANS 2021 Conference, 1\u20135.<\/li>\n
  4. Zhang, L., et al. (2020). Temperature-Stabilized 940 nm Single Bar Diodes for Underwater Sensing Applications. Optical Engineering<\/em>, 59(12), 126107.<\/li>\n<\/ol>\n
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    Hangzhou Brandnew Technology Co., Ltd.<\/a>
    Hangzhou Brandnew Technology Co., Ltd. is one of the leading 940nm single bar diode laser manufacturers and suppliers in China, has a professional factory which manufacturers high quality 940nm single bar diode laser and sells at competitive price. Welcome to wholesale our products made in China.
    Address: 17F,Building 2, Aoqiang Mansion, No. 6 Xiyuan 5th Rd,310030 Hangzhou,China
    E-mail: admin@brandnew-china.com
    WebSite:     https:\/\/www.brandnewdiode.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

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