Md Arafat Hossain and colleagues from the University of Sydney have developed a smartphone-based ultraviolet laser beam spatial profiler (Opt. Lett. 40, 5156–5159; 2015). Their device, which is low cost thanks to the use of three-dimensional mount printing and the competitive pricing of mobile phone technology, is able to measure a laser beam's spatial profile, output power, divergence and beam quality factor, with all information displayed on the phone's screen and optionally transferred conveniently via the internet.

Credit: OSA

In their set-up, the ultraviolet beam strikes a 4 cm × 4 cm phosphor glass plate that is normal to the beam's propagation direction. The phosphor plate downconverts the ultraviolet light to visible wavelengths, which is imaged onto the phone's CMOS camera, located 3 cm downstream, via an external lens (thickness, 10 mm; focal length, 10 mm). The phone used is a Kogan 4G, which has an 8 MP rear-facing camera with a maximum signal-to-noise ratio of around 55 dB. Neutral density filters (or other suitable attenuators) are used to avoid saturation of the CMOS sensor. The software to display the beam and its parameters runs on the phone itself. The team evaluated the performance of the scheme by characterizing two ultraviolet lasers: a continuous-wave Ar+ laser (244 nm wavelength) and a pulsed ArF laser (193 nm wavelength, 30 Hz repetition rate, 15 ns pulse duration). Experimental variation in the measurements was comparable to commercial beam profilers.

John Canning, corresponding author for the manuscript, told Nature Photonics that the idea worked surprisingly well, and that the main challenge was to ensure measurements could be made both rapidly and reliably. The current system employs a phone running an Android operating system. Canning explained that the Android user-base is several times larger than that of Apple's iOS phones, and that the Android platform may have programming advantages. However, he notes that the same device could be achieved on an iOS system.

“We have already demonstrated combined spectrometer instrumentation with both absorption and fluorescence, so the next direction will be combining multiple instruments onto a single platform,” Canning remarked. “For this particular example, adding spectroscopy and linewidth measurements for lasers is potentially feasible. [...] It is also possible to combine laser characterization during spectroscopic analysis so that the beam profile is always understood during excitation of the source being studied.”

In their manuscript, the researchers explain that the detection range could be extended to, for example, the near-infrared regime. Canning also noted that the instrument could be made smaller to accommodate other capabilities. There are plans to commercialize some of the team's smartphone instrumentations.