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Compact, high-power, frequency-converted diode laser systems

Periodic Reporting for period 1 - CoDiS (Compact, high-power, frequency-converted diode laser systems)

Reporting period: 2015-06-01 to 2015-10-31

Objectives:

Visible lasers are of interest to a wide variety of industries, including life science, lighting, medical diagnos-tics, laser pumping, and scientific applications. Existing laser technologies do not offer the combination of intrinsic stability, low noise, high beam quality, high power, and wavelength tuneability of the Norlase Tapered Doubled Diode Laser platform.
Norlase is a spin-out company set up to develop and commercialize a new class of visible lasers, tapered diode doubled lasers (TDDL), based on award-winning technology invented at Technical University of Denmark (DTU). Norlase’s top management – including the CEO and the five Board Members – have longstanding experience and a very strong track-record within the photonics and lasers industry, namely in developing start-ups into large, successful businesses and/or heading some of the world-leading companies in the sector.

The TDDL is a unique and simple platform technology that vastly reduces cost of visible lasers for high-volume applications. Based on patented and award-winning technology, the overall objective of Norlase is to manufacture a new class of compact, stable, low-noise visible lasers in the 1 to 20 W output power range that provides designers of OEM equipment unique opportunities in terms of performance and cost effectiveness. The Norlase mission is to become world-leading supplier of visible continuous wave lasers in this power range. Norlase aims at establishing itself as a laser production company based in Europe – thus creating significant tangible economic impacts, namely in terms of job creation, particularly highly-skilled engineering and highly-specialized technical jobs. Despite being a start-up company, Norlase has already completed prototype sales including delivery to several market leading OEM customers, raised BA and VC capital and finally Norlase has won several national grants (incl. EUDP and the Market Maturation Fund) in fields including laser-based lighting and life science applications.

The novel, compact laser is based on semiconductor lasers (diode lasers) and this technology has potential to yield low-cost, reliable products. In market segments representing a few hundred units per year for Norlase, as those mentioned above, the unit cost may be reduced drastically, i.e. a step-change cost-wise. For our OEM customers this step-change will expand existing markets and additionally open new market opportunities. Hence, the Norlase technology provides a huge business opportunity to establish a leading laser manufacturer within Europe thriving on a technology (semiconductors), where Europe holds a strong and world-leading position.

The key objectives for the overall innovation project are:

• to complete the validation of Norlase’s platform technology and to demonstrate and prepare market roll-out of the initial product portfolio – particularly in wavelength regions where development and initial demonstration have already been reached, i.e. green (532 nm) and blue (488 nm);

• to complete 10,000 hrs life-time and reliability tests of products at 532 nm (2W and 4W) and at 488 nm (2W) in order to have a fully certified product for OEM customers;

• to remove the need for expensive optical isolators by innovative designs of semiconductor laser;

• to plan the expansion of Norlase’s platform technology into wavelength regions that cannot be reached by competing technologies, namely yellow, where there is huge market potential.

Accordingly, the main objectives for the CoDiS feasibility study (Phase 1) was:

• to map out market segments in a detailed business plan, where Norlase technology makes the above-mentioned step-change cost-wise allowing sustainable growth of the company, and to prepare activities for Phase 2 project,

• to complete the design phase for electronics, control software, and user interface,

• to elaborate the strategy for further reducing the number of components that in turn
Technical feasibility study results

1. Control system and interfaces:
The TDDL requires cost-effective and easy-to-operate driver electronics, that can be controlled via a simple user interface. In this task, design of the modular driver electronics for the laser head and the control software is completed.

Laser driver:
In collaboration with an electronics supplier, a one-box solution to control the laser head was developed. This solution is called “AuroraOne”. A picture of the electronic driver can be seen on figure 1.

The controller is in essence 5 separate electronics controllers combined into one. The 5 separate drivers are as follows. Two current controllers (power supplies) to control the current injected into the tapered diode laser, and three temperature controllers that control the temperature of the laser and the two non-linear crystals. The unit also contains an additional temperature monitor used for recording the case temperature of the laser head. Finally, the controller includes a circuit for monitoring the response from a photodiode inside the laser head. The response from this photodiode can be used to calculate the output power from the laser. This feature can either be used to monitor or stabilize the output power from the laser.

On the front of the AuroraOne a power switch turns the device on/off. A key switch disables/enables the laser output. The AuroraOne is connected to the laser head with a single custom made laser cable connected to the back of the device. Also on the back of the device, an external interlock circuit can be connected to the controller, enabling safety shutdown of the laser if needed. Furthermore, the controller can drive an external fan, if forced air-cooling of the laser head is needed.

A USB port on the back of the AuroraOne is used for controlling the driver with a PC.
Compliance testing of European and US regulations were performed with an external regulatory and compliance laboratory. Test certificates have been issued, showing that the AuroraOne complies with the following standards:

a) CE EN 61010-1:2010 – Safety requirements for electrical equipment for measurement, control and laboratory use.

b) CE EN 61326-1:2013 – Electromagnetic compatibility (EMC) requirements for electrical equipment for measurement, control and laboratory use.

c) FCC CFR 47 Part 15 – Emission regulations on electronics device sold inside the United States.

The current status of the AuroraOne is that the first 3 working units have been developed, built and delivered. These units are currently undergoing tests. Minor bugs are identified and fixed. An additional order of 15 devices is placed with the supplier for delivery in Q1 2016.

Control software
To communicate with the AuroraOne and thereby with the laser head, a LabView-based program is made. This program monitors and controls all relevant parameters, such as temperatures, currents and laser output power. All the parameters of the laser are preset, and the laser is turned either on or off by pressing the “start” and “stop” laser button.
Laser emission can be enabled in two modes of operation, “constant current” and “constant power”. In constant current mode, the currents to the laser diode are fixed. External and internal influences on the laser head, such as room temperature or diode ageing are not compensated for. The output power will therefore be fluctuating slightly. In constant power mode, the photodiode inside the laser head is used to monitor the output power. The current setpoints are then dynamically adjusted to obtain a constant and stabile laser output.

Included in the software is an algorithm to turn on the laser in a controlled manner. The algorithm ensures that the laser operates in a “correct” mode of operation when emission is enabled. This ensures that the laser will run for a longer time and not fail after a short time of operation.

The software program constantly monitors a number of
Progress since grant agreement
The finding in our feasibility study confirms our hopes and expectation in the technology, the product and the market. The project has not only confirmed and improved the concept, but also led us to set more ambitious objectives for the innovation project and advanced our road map and market expectations. During the project, market traction has increased, both on the existing market for pump lasers and on the new market for medical lasers.

More ambitious innovation project objectives
When we initiated the feasibility study project, our aim for the exploitation of our technology platform was to exploit the market for green lasers, and the objectives for the innovation project (phase 2) set out was:

• to complete the validation of Norlase’s platform technology and to demonstrate and prepare market roll-out of the initial product portfolio – particularly in wavelength regions where development and initial demonstration have already been reached, i.e. green (532 nm) and blue (488 nm);

• to complete 10,000 hrs life-time and reliability tests of products at 532 nm (2W and 4W) and at 488 nm (2W) in order to have a fully certified product for OEM customers;

• to remove the need for expensive optical isolators by innovative designs of semiconductor laser;

• to plan the expansion of Norlase’s platform technology into wavelength regions that cannot be reached by competing technologies, namely yellow, where there is huge market potential.

Thus, the last of these objective was included to have ambitious goals for scalability of the TDDL platform into scales beyond the target for innovation project. As described above, the progress during the feasibilty study activities on the expansion of the technology into the yellow wavelength area convinced us that we should aim directly for this opportunity in the innovation project. Thus, rather than including this as an option plan for expansion, we will move directly to the exploitation of this wavelength domain as the main aim of the innovation project. However, as we keep setting new goals for the expansion of the platform, we will in the innovation project include new ambitious goals for the scalability.

Unchanged concept
The concept behind the technology remains unchanged as we move into the yellow wavelength domain. As it is clear from the descriptions of the TDDL platform above, it is the same patented platform that are used to achieve the yellow wavelengths as the green and blue.

However, the feasibility study has led to improvement to the platform. One of the goals of the study was to find a solution that could obsolete an optical isolator a bulky, a costly component in the design. As described above, the feasibility study has substantiated that a combination of two solutions is a viable path to eliminate this component, which will improve the margin of the product even more. These solutions will need to be further explored and developed to capture the cost-saving potential.

New markets and increased impact
From the perspective of our platform, the change to new wavelengths is thus a continuous innovation of the TDDL technology. However, as described, moving into yellow domain gives us ability to disrupt the market even more compared the initially foreseen target market of green and blue lasers.

At the beginning of the feasibility study, with the TDDL platform applied to green domain, the market for pump lasers was identified as the best market for introduction. This is still the case for this wavelength. However, with the proven feasibility of extending the platform into the yellow domain, even more interesting segment becomes available, namely medical applications such as ophthalmic (eye-treatments) application and dermatology (skin treatments).

Thus, as we change from from green to yellow lasers, we perform a step-change in our route to market strategy. Accordingly, instead of the foreseen pump laser markets, we will in the inno
Figure 1, picture of AuroraOne electronic driver