Technology

PCSELs are the future of laser production

PCSELs are a new class of semiconductor laser. They utilise a 2D grating structure which scatters light linearly and orthogonally. This makes PCSELs the only laser where feedback is in-plane and light emission is out of plane, emanating from the laser’s top surface.

Out of plane, orthogonal, surface emission offers a huge cost advantage for lasers, as it makes them easy to package and incorporate into PCBs and electronic assemblies. Out of plane emission is enabled and stabilised by our 2D grating structure (photonic crystal), creating feedback and single mode emission. The PCSEL structure provides advantages in data rate, wavelength and power performance when compared to equivalent EELs or VCSELs.

Vector Photonics’ PCSELs deliver low cost, high-volume, robust build, broad wavelength range and high power.

“Our PCSELs produce the speed performance of EELs and VCSELs, whilst their tested and packaged cost is 50% that of EELs and they deliver over 10x the power of VCSELs.”

Neil Martin, CEO, Vector Photonics

The laser technology evolution.

Fabry Perot lasers are the original, semiconductor laser technology. The laser feedback and emission are both in-plane, so light comes out of the end of the laser and the gain reflection is produced by facet mirrors. DFB lasers also have in-plane feedback and emission, but this time the gain reflection is produced with a grating structure.

VCSEL technology has out of plane gain and emission, where the light emits from the top surface of the laser. This makes both the test and packaging of the lasers much cheaper than EELs.

The PCSEL is the only laser using in-plane feedback and out of plane, surface emission. Test and packaging remain cheaper, like VCSELs, but the PCSEL structure provides advantages in data rate, wavelength and power performance when compared to equivalent sized EELs or VCSELs.

PCSELs – low cost with high speed and power – 3 in one!

PCSELs have it all! They deliver low cost with high speed and power. All other current laser technologies offer only two of these three, key characteristics in one device.

VCSELs (Vertical Cavity Surface Emitting Lasers) compromise power for low cost and high speed. EEL’s (Edge Emitting Lasers), including FP (Fabry-Perot) and DFB (Distributed Feedback) lasers offer speed and power, but are expensive to make.

PCSELs have other advantages too. They emit light from the top surface, like VCSELs, making them easy to package and incorporate into PCBs and electronic assemblies. They are also made in a similar way to EELs, so existing, experienced, supply chain capability and capacity can be utilised in their production. Vector Photonics’ PCSELs can be made at any wavelength, so can be used to address a wide breadth of applications.

EELs compromise
cost and ease of assembly

EEL Lasers (Edge Emitting Lasers) have been in production for more than 40 years, where they have proven their reliability and longevity in telecoms and data systems.

FP (Fabry-Perot) and DFB (Distributed Feedback) lasers are both types of legacy, semiconductor EELs. EELs offer high levels of single-mode performance, both from optical spectrum range and power perspectives. However, EELs have two significant disadvantages. The first disadvantage is that they must be precisely aligned and handled to be integrated into systems. This is because single-mode light is emitted from the edge, not the front, meaning the lasers must be precisely aligned within subassemblies to re-direct the light into the correct direction for optical fibres or free space. The second disadvantage is that they require complex manufacturing and testing processes. The semiconductor wafers must be split into bars and finished on each side with reflective coatings. Each laser must be tested at bar level before being ‘singulated’ into individual laser devices for system integration. These multiple processing and testing steps increase cost and reduce yield.

VCSELs compromise
wavelength range and power

VCSELs (Vertical Cavity Surface Emitting Lasers) were first produced in the early 1990’s. They have limited operational wavelengths due to the manufacturing challenges caused by the various material systems required for multi-wavelength operation.

A VCSEL is produced by having two Bragg stacks above and below the active region of the laser. The Bragg stack comprises layers of two materials of differing refractive index ‘grown’ on top of one another. The number of layers, and therefore periods and the refractive index contrast, gives rise to the reflectivity. A high number of periods gives high reflectivity, and high index contrast increases reflectivity per layer.

The VCSEL grating structure also has inherent limitations to the single mode, power levels that can be produced. So, although VCSELs can achieve high speeds and can be produced cost-effectively, their limited single mode performance makes them unsuitable for high-speed datacoms and long-distance telecoms. These limitations also restrict their use in sensing applications to relatively short distances.

Laser technology comparison chart

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