Chirped Mirrors (Stocks)

What are Chirped Mirrors and How They Work

Chirped Mirrors are a kind of dielectric laser mirrors made for ultrafast femtosecond lasers to provide broadband dispersion compensation. Chirped mirrors have negative group delay dispersion (GDD). Unlike conventional dielectric laser mirrors, chirped mirrors are manufactured via depositing a multilayer optical coating with a non-uniform (chirped) layer thickness distribution on fused silica glass substrates. 

This is basically how a chirped mirror works: by designing the thickness and material (i.e., refractive index) of the mirror coating film stack, shorter wavelengths reflect closer to the surface, while longer wavelengths penetrate deeper before reflecting. The spatial separation of reflection points across the spectrum introduces a wavelength-dependent group delay, allowing the mirror to compensate for or introduce dispersion. This is how chirped mirrors manipulate the group delay dispersion (GDD).

Applications of Chirped Mirrors

Dispersion Compensation in Femtosecond Lasers

In femtosecond lasers, it is essential to keep the extremely short pulse durations integrated and minimize temporal broadening. Due to the dispersive nature of the glass substrates, different wavelengths have different refractive indices, which leads to the accumulation of positive GDD when lights travel in optics. Chirped mirrors are used to introduce negative GDD, thereby compensating for the dispersion. 

Chirped Pulse Amplification (CPA)

In high-power ultrafast laser systems, direct amplification of short pulses can easily damage optical components due to excessive instantaneous power or cause unwanted nonlinear effects on the laser gain media. Using chirped mirrors, the chirped pulse amplification technique can prevent this problem by stretching the pulse duration first and compressing it back later via temporal control.

Chirped mirrors can be used or applied for:

Typical applications of chirped mirrors include: 

• High-resolution microscope (e.g., multiphoton microscope)
• Ultrafast spectroscope
• Precision micromachining
• Pulse compressors in CPA (Chirped Pulse Amplification) systems
• Optical parametric chirped-pulse amplification (OPCPA) setups

Hangzhou Shalom EO: Trusted Supplier of Chirped Mirrors

Hangzhou Shalom EO provides stock and custom chirped mirrors optimized for use in femtosecond laser systems. The standard chirped mirrors, featuring >99.9% high reflectivities and laser induced damage threshold of 4J/cm2@1030nm, 200ps, 100hz, are excellent for Ti:sapphire and Ytterbium ultrafast femtosecond lasers, where the mirrors can be integrated into chirped-pulse amplifier systems and ultra-broadband laser oscillators. This page specifies our off-the-shelf chirped mirrors. Shalom EO’s off-the-shelf chirped mirrors are available at 1/2” or 1” diameters, and are designed to offer -100fs2, -500fs2, or -1000fs2 negative GDD values at 0° to 10° angle of incidence, where the small AOIs allow multiple reflections. In our labs, the GDD curves are tested using the Ultrafast Innovations GOBI white light interferometer. As a byproduct of GDD, third order dispersion (TOD) of the chirped mirrors is also carefully evaluated to reach an ideal balance between GDD and TOD.

Besides, we can also provide both off-the-shelf and custom matched chirped pairs. Compared to single chirped mirrors, chirped mirror pairs provide improved GDD oscillation.

Application Notes:

1. The figure below shows a typical design structure of a Ti:Sapphire femtosecond laser system, including a pumping source, Ti:sapphire crystals, laser cavity mirrors, output couplers, optical modulators, and chirped mirrors.

Specifications:

Curves:

1. Reflection and GDD Curve of 1000-1060nm, -100fs2 GDD, 0-10deg AOI Chirped Mirror

2. Reflection and GDD Curve of 1000-1060nm, -500fs2 GDD, 0-10deg AOI Chirped Mirror