German team develops micro diode pumped laser for ophthalmology, which is more c

It is well known that the detachment of the retina of the eye can lead to visual impairment, even blindness. In recent years, laser coagulation has become a mature method, which is used to treat retinal holes or cracks with laser spots, and has made great efforts in treating diseases such as diabetes retinopathy and age-related macular degeneration.

However, it is a pity that the current system of laser coagulation is quite expensive, and its light source is usually limited to several laser wavelengths. Recently, the Ferdinand Braun Institute (FBH) in Berlin, Germany, announced the successful development of a semiconductor based, efficient and reliable laser source, which is expected to reverse this situation.

(Photo source: Ferdinand － Braun － Institute)

It is reported that this laser source can be flexibly adjusted to the optimal wavelength and bring significant cost benefits. It is a miniaturized and robust laser source in the near infrared (NIR) wavelength range, with high spectral radiance and very suitable for industrial applications. Each of its light sources consists of a pump laser, and the light in its near-infrared spectrum can be converted using nonlinear crystals - doubling the frequency (second harmonic generation SHG) will halve the wavelength. Therefore, the laser can be emitted in the visible spectral range.

At present, the laser solidification systems on the market specially use 532 nm and 577 nm wavelengths. Therefore, FBH hopes to break the original limitation and enable its developed pump module to achieve these set wavelengths within the yellow green spectrum. For ophthalmic applications, the development of 577 nm laser is particularly valuable, because oxygen rich blood pigment (i.e. oxyhemoglobin) will have the strongest absorption effect in this wavelength.

The researchers of Ferdinand Braun Institute (FBH) successfully realized a miniature diode pumped laser covering 400 nm - 600 nm spectrum by using a combination of miniaturized optical modules (as pump sources) and efficient second harmonic (SHG). In contrast, the wavelengths of previous solid-state laser systems are limited to 532 nm, 561 nm, 577 nm and 586 nm laser product lines.

In addition, the laser diode and amplifier can also be mass produced on the wafer, thus reducing the cost. For example, 400 such active elements can be mounted on a 3-inch wafer with a diameter of 76 mm.

It is reported that narrowband pump sources at 1154 nm and 1064 nm have high optical output power and excellent beam quality, which simplifies the subsequent frequency doubling in the yellow green spectrum range. This reduces cost and weight compared to the more complex laser sources used to date for laser solidification. And because of its portable and flexible use, this micro diode pumped laser system can be successfully applied in the outpatient environment.

In order to prove the applicability of optical modules as pump sources, scientists from the Ferdinand Braun Institute (FBH) in Berlin, Germany, developed a prototype module with independent laser beam generation (main oscillator - MO) and power amplification (power amplifier - PA) functions.

It is reported that they have integrated a commercial micro isolator between the two components to completely protect the laser (MO) from external feedback. In SHG crystal with waveguide, external feedback may be very high (feedback rate>1%), and can significantly interfere with the main laser oscillator (MO).

Although the area is only 25 mm × 25 mm, the module achieves an optical output power of more than 8 watts in continuous wave (CW) mode at 1064 nm and 1156 nm. At the same time, they achieve a high beam quality of M2<2 and a spectral line width of<5 MHz. The research team points out that this performance can also be transferred to other wavelength lasers.

Source: OFweek