The new lasers open the way for the integration of optical and electrical components on gain chips, a breakthrough that might enhance computing speeds and data transmission rates considerably. Optical communications, spectroscopic methods, and frequency metrology have all been made possible by tunable lasers with small spectral line widths.
Gain chips are semiconductor optical devices used in external cavity laser diodes as the optical gain medium. It is used as a TLS (Tunable Light Source) with a wavelength selection filter. Due to the nature of the technology, the semiconductor laser source is an ideal contender, since it offers the advantages of size, weight, and power, as well as cost and production scale.
In this blog, we have covered all of the significant aspects of gain chips. So let’s get started!
What is Gain Chip?
A gain chip is a crucial component in the development of tunable diode lasers or high-stability external cavity diode lasers. It serves as a tunable light source with a frequency selection filter, such as a diffraction grating, to modify the oscillation wavelength.
Gain chips resemble laser diode chips but differ in having a thick anti-reflective coating on one or both faces, which significantly reduces or eliminates self-lasing. The diffraction grating reflects light of the desired wavelength back along the incident beam, and the grating can be rotated to scan the wavelength. The output laser beam is typically a zero-order diffracted beam.
Types of Gain Chip
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One Side Optical Access
Optical access on one side gain-chip is an excellent component for use in systems where the output power is uncoupled from the external cavity. It is included with the to-can package.
Type A:
A typical gain chip is characterized by a straight stripe extending to the facets, featuring strong reflecting HR and extensive antireflecting AR coatings. This design is the most cost-effective external cavity diode laser, equipped with a high NA aspheric lens that provides excellent coupling to both the external cavity and the back. Additionally, this type of gain chip offers relatively low gain spectral ripple removal compared to other types.
Type B:
A curving stripe with a normal side HR and thick AR coating on the sloping side distinguishes the Type B gain chip. It provides extremely low reflection, enabling the suppression of self-lasing and minimizing gain ripples that could distort the output beam. However, this design makes collimation challenging and negatively impacts back coupling efficiency.
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Two Sides Optical Access
Optical access on both sides Gain-chips can be utilized in optical amplification schemes or in techniques that allow for direct power out coupling from the Gain-chip.
Type C:
This type of gain chip features a curved stripe and deep AR coating, whereas, the normal side has a few percent reflections. This design provides a high output power and a decent output beam based on the system setup and desired output power. The wavelength selecting feedback must be on the angled side, while the output power must be on the normal side.
Type D:
Type D gain chip has a tilted stripe on both sides with a deep AR and is commonly used for complex optical systems to fulfill high-reliability requirements. The ISO verifies that production is based on rigorous design, fabrication, and testing, all of which are supported by test results.
Applications of Gain Chip
A gain chip is utilized as a laser in an external cavity (EC) tunable laser configuration and provides broadly tunable lasers at various wavelengths due to its active region design, cavity length, and essential performance characteristics. It is widely used in the telecom sector as a tunable light source (TLS), where it can alter the oscillation wavelength using a diffraction grating.
Let’s take a look at some of the most fascinating applications of gain chips in a brief.
A. As an External Cavity Type TLS
In an external cavity laser diode, the gain medium is a resonant mirror on the outside of the semiconductor component. In order to regulate the oscillation frequency, a diffraction grating can be used.
B. As a Silicon Photonics Tunable Light Source
In communication networks with speeds reaching 100Gbps, coherent optical fiber communications with ultra-high-speed digital signal processing are used. This has emphasized silicon photonics technology, which employs a silicon chip that contains an optical waveguide, an optical modulator, and a wavelength filter. The gain medium in silicon photonics is a Reflective SOA (RSOA) gain chip.
In addition, while choosing the gain chip, make sure you take care of the following criteria:
- Gain and power
- Tuning Range
- Manufacturability
- Reflectivity & design
All these factors are very critical when choosing the perfect gain chips. Make sure, you take note of each one.
Features & Performance
Gain chips are designed to provide strong optical gain over a wide wavelength range. In an external cavity laser system, the gain chip functions as the laser’s primary gain source. It is available in chip or submount form, with a high reflectivity (HR) coating on the standard rear facet and a low reflectivity anti-reflecting (AR) coating on the tilted front facet to optimize performance and minimize unwanted reflections.
Let’s take a look at some key features of the gain chip:
- Excellent beam divergence for fiber
- HR/AR facets are coated optically
- High output power and broad bandwidth
- Active layer structure in quantum wells
- Customizable in silicon photonics application
As this blog has shown, the gain chip is a significant component in lasers. We’ve covered everything you need to know about it, its components, and its features with its applications. To know the advanced technical details of it, check our product page.
Inphenix develops and manufactures lasers and light sources for use in cutting-edge medical, telecommunications, sensing, and measurement applications. You can contact us for additional information about our products.
