ZT vs T Dichroic Mirrors
Choosing the Right Option for Your Optical System
When designing a fluorescence or analytical optical system, the dichroic beamsplitter plays a central role. It reflects excitation light toward the sample while transmitting generated fluorescence emission light toward the detector. Small differences in dichroic design can significantly impact signal strength, channel separation, and overall system performance.
A dichroic is designed to reflect one spectral region and transmit another, with a defined transition between the two. In fluorescence systems, this typically means high reflection in the excitation band, high transmission in the emission band, and a well-controlled transition edge.
ZT Dichroics
ZT dichroics are optimized for demanding fluorescence applications requiring steeper spectral transitions, strong channel separation, and tight edge control. They are often selected when minimizing cross-talk is critical or when working with spectrally adjacent fluorophores. Choose ZT dichroics when using closely spaced fluorophores, optimizing for high-sensitivity detection, or when building a multicolor platform where maximum channel separation is required.
T Dichroics
T dichroics provide robust and versatile performance across many standard configurations. They are well suited for systems with comfortably separated excitation and emission bands and offer a strong balance of performance and cost efficiency. Choose T dichroics when excitation and emission bands are well separated, system demands are moderate, and strong performance with cost efficiency is a priority.
Breaking down Chroma’s T and ZT series dichroic filters
In this next section, we will break down the specifics of Chroma Technology's T and ZT series dichroic mirrors. We aim to simplify the naming convention for you and highlight the distinct features of these mirrors.
You will find a summary of their differences, an overview of the wavelengths they represent, a table of key terms, and an explanation of surface flatness specifications. Should you need more information, additional resources are provided throughout the article.
Overview of T and ZT Dichroic Filters
| T Dichroic Mirrors | ZT Laser Dichroic Mirrors |
Naming Convention | T###lp | ZT###rdc |
Purpose | Standard widefield dichroics for fluorescence microscopy | Laser specific dichroics |
Wavelength (###) | Represents the 50% transmission point | Represents the laser wavelength at which light is reflected or transmitted (dependent on dichoic type) |
Surface Flatness | Originally no specific flatness spec, but offered in ultra-flat specs (UF1, UF2, UF3) | Always offered in ultra-flat specs (UF1, UF2, UF3) |
50% Transmission Point | At specified wavelength (e.g., 560nm for t560lp) | Typically at a slightly longer wavelength to reflect the full range of the laser light (e.g., around 577nm for ZT561rdc) |
Material | UVFS | UVFS |
Specified Wavelengths in T and ZT Dichroics
At Chroma, we employ a specific naming convention for our optics. The numerical values in our dichroic mirror names represent a specific wavelength in nanometers (nm).
In our T series dichroic mirrors, this number corresponds to the 50% transmission wavelength.
In our ZT series laser-reflecting dichroic mirrors, this number corresponds to the wavelength at which the filter is designed to reflect light.
In our ZT series laser-transmitting dichroic mirrors, this number corresponds to the wavelength at which the filter is designed to transmit light.
Table of Key Terms
To help decode our dichroic mirror names, here's a handy table of key terms:
Term | Meaning |
T | Dichroic Mirror |
ZT | Laser Dichroic Mirror |
### | Wavelength in Nanometers |
lp | Long Pass Mirror |
rdc | Reflecting Dichroic |
rpc | Reflecting Polychroic |
For more in-depth definitions of the nomenclature used to name our dichroic mirrors, please see our comprehensive glossary page.
Surface Flatness in T and ZT Dichroics
All of our ZT series dichroics are offered with our ultra-flat specifications. These filters include the UF designation, which corresponds to their thickness and flatness values. These values are shown in the table below:
Spec | Thickness | Surface Flatness |
UF1 | 1mm | 2 waves/inch |
UF2 | 2mm | 0.5 waves/inch |
UF3 | 3mm | 0.25 waves/inch |
Our T series dichroic mirrors were initially offered without surface flatness specifications. However, in response to microscopy's evolving demands relative to surface flatness, we've adapted a subset of our T series dichroic mirrors to include ultra-flat specs.
These ultra-flat T series mirrors are identified with the same UF options and designations as shown above.
Conclusion
Understanding our dichroic mirrors isn't too tough once you know what the names mean. Both our T and ZT series are designed to give you the best performance for your specific needs.
If you still have questions or need more information, don't hesitate to reach out. We're here to help you. Contact us anytime.
Frequently asked questions
Does it matter which dichroic I use with my excitation and emission filters?
Yes, the correct dichroic (or polychroic) mirror selection is very important. The job of the dichroic mirror is to reflect the excitation light to the sample and transmit the emission light to the detector.
Can I use a longpass filter as a dichroic?
No. All of our filter and dichroic designs are very angle-sensitive. Our emission filters are designed for a zero-degree angle of incidence (AOI) and dichroics are designed for a 45-degree AOI (unless otherwise specified). Changing this angle will drastically shift the spectral performance of the part.
