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Rohm Stretches LiDAR Range With New High-Power Laser Diode

December 04, 2023 by Jake Hertz

The 120-W infrared high-output laser diode can offer higher precision for distance measurement and spatial recognition in 3D ToF systems.

Light sources are at the heart of every LiDAR system, and Rohm has recently upped the quality of such offerings with a new high-power laser diode. The newest offering expands Rohm's existing portfolio of patented diode technology: the company released a 25-W laser diode in 2019 and a 75-W laser diode in 2021. Now responding to higher output demands, Rohm has developed a 120-W high-power laser diode, expressly distinct from conventional laser diodes. What sets this device apart from the competition? 

 

RLD90QZW8

Rohm claims its new RLD90QZW8 laser diode offers a narrow emission width of 270 µm—more than 6% less than competing laser diodes, which have 290 µm or 360 µm emission widths. 
 

Rohm's High-Power Laser Diode 

Rohm engineered its RLD90QZW8 (datasheet linked) to emit high light output with a short current driving time. These features make it useful for LiDAR-based object detection tasks. Operating at a 905 nm wavelength, the diode stands out with an optical output power of 120 W (pulse) and a narrow light emission pattern provided by a Φ5.6 metal stem​.

A key feature of this diode is its low wavelength temperature dependence. According to Rohm, the RLD90QZW8 was developed with a wavelength temperature dependence of 0.10 nm/°C or less, which is 66% less than the 0.15 nm/°C developed for their 75-W products. This reduced temperature dependence enhances measurement accuracy and range in LiDAR applications.

 

Optical characteristics of the 90QZW800X-E

Optical characteristics of the 90QZW800X-E. 
 

Other noteworthy performance metrics include a max optical output power of 145 W at a forward current (If) of 38 A. It also has a peak pulse wavelength of 915 nm, an operating voltage of 13 V (typ), and beam divergence measurements of 11 def and 20 degrees measured parallel and perpendicular to the beam,​​ respectively. 

 

High-Power Laser Diodes for More Precise LiDAR

High-power laser diodes are an integral part of how LiDAR works. These diodes must emit high light output within a short current driving time, also known as pulse width. Operating predominantly in the 905 nm wavelength band, these diodes must be highly reliable and provide superior beam quality and stable temperature.

 

Resolution of a high-power laser diode versus a conventional laser diode

Resolution of a high-power laser diode versus a conventional laser diode. 
 

High-power laser diodes emit a concentrated beam of light to illuminate objects. The LiDAR system then measures the time it takes for the reflected light to return, thereby determining the distance and shape of the object. The power of the laser diode is critical in this process; a stronger and more focused light beam yields longer-range detection and higher-resolution imaging. 

According to Rohm, high-power laser diodes perform better than conventional laser diodes, in part because they are not as dependent on wavelength temperature. Rohm's RLD90QZW8 model, for instance, has achieved a temperature dependence of less than 0.10 nm/°C. This improvement enables system designs to have a narrower wavelength range, which in turn enhances signal-to-noise ratios and provides more accurate measurements at greater distances. Such advancements in temperature stability contribute significantly to the performance and reliability of LiDAR systems.

 

A Boon for Autonomous Vehicles and Robotics

LiDAR is only as effective as its underlying light sources—and high-power laser diodes provide some of the highest performances in the field. Rohm asserts that its new diode offers better power, resolution, and SNR than any of its previous solutions, making it a good fit for autonomous vehicle and advanced robotic designs.

 


 

All images (modified) used courtesy of Rohm.