Frequently Asked Questions

I have a lens/filter/mirror/optic that I purchased from CVI Laser Optics and I want to clean it. What cleaning methods are recommended for my item?

The recommended cleaning methods are dependent on the type of optic and its coatings. test

You can download the recommended CVI Laser Optics cleaning procedures document Cleaning Methods (PDF).

The first part of the document describes five separate cleaning procedures with step-by-step instructions. The second part of the document lists which procedures should be used for which component.

You can also download this article Cleaning Optics (PDF)  which explains the importance of the cleaning process to improve both the lifetime and performance of optics. Proper materials, techniques and handling procedures should be used to minimize the risk of damage.

Helpful Light Beam Definitions

Continuous Wave

Laser power is fixed or variable, but not delivered in a discrete pulse envelope.


Laser energy is delivered in a single discrete pulse at a specified repetition rate.


The average power of a continuous wave (cw) laser beam expressed in watts (W).

Energy per Pulse

The energy of an individual pulse expressed in joules (J).

Pulse Repetition Rate

The rate at which pulses are repeated in a uniformly pulsed train of pulses expressed at the frequency of repetition of the pulses in the unit of hertz (pulses per second, Hz).

Gaussian Criteria

The definition as used in the ANSI Z136.1 Standard for both beam diameter and beam divergence, require that these quantities be measured at the 1/e power point (63.2%) on the ideal Gaussian beam intensity profile. Note that most laser equipment manufacturers specify these beam properties at the 1/e2 power point (86.5%), which is a factor of 1.414 larger than the 1/e power point.

Beam Dimension

Beam size (typically diameter) in millimeters, measured on the longest dimension.

Beam Divergence

Change in beam size with respect to the distance measured in milliradians.


What is the index/transmission of a certain optical material at a certain wavelength?

Typical index and transmission values for our optical materials can be found in our catalog. This link will open the appropriate section  Material Properties (PDF).

I want to purchase one of your optical products, but the coating I want is not listed on the website as available for that product. Can I still get the coating I want?

Most of the time, yes. The optic & coating combinations shown on the Buy-Online section are our most popular ones, and are the most likely to be readily available. Our full selection of antireflection and high-reflection coatings can be applied to our line of optics for an additional fee. For coating recommendations, availability, and pricing please contact one of our Applications Engineers at

What is the damage threshold for your anti-reflective and mirror coatings?

CVI Laser Optics has tested the majority of our coatings for their damage threshold specifications. We understand that it is important to our customers to know what this limit is in order to preserve the integrity of their optical systems.

This link will open the appropriate Coatings (PDF) section of our catalog. Below each coating, there is a typical damage threshold listed. When coatings are very similar in composition, there may be a reference to another coating for its damage threshold. Please note that all the values given are for reference only and do not imply a guarantee.

There are many different applications for the coatings, so we tried to test them with a common laser for the specified range of the coating. They were typically tested using a pulsed 1064 nm laser and its harmonics. Unfortunately, we could not possibly test them for all different configurations, including continuous (CW) lasers. There are simply too many parameters that affect the damage threshold of a coating. Therefore, we do not have any other data than what is specified in the catalog and there is not a simple formula to determine how a different wavelength might respond.

I was looking through your concave reflectors and your spherical mirrors but couldn't find the correct radius of curvature that I need. Do you make custom reflectors?

Yes, we can! Our ability to modify includes edging diameters down and cutting to square or rectangular shapes. This includes lenses (both spherical and cylindrical), mirrors, and filters (excluding the interference filters).

There are a few rules of thumb to follow when modifying standard pieces:

The standard tolerance for modifications is ±0.25 mm (±0.01"). If a customer needs a tighter tolerance, it must be specified.

A standard lens can be edged down to a diameter that is no less than twice the center thickness of the lens. For example, the smallest we could edge a beginning diameter of 30 mm and center thickness 8.4 mm is down to 17 mm.

A mirror can be modified, but the flatness cannot be maintained to the original specification because stress is induced when a piece is modified. We can also use CNC processing to create 1-off pieces in a myriad of size and radii options. And, finally, we make custom lenses in larger batches for many customers and applications.

Can CVI Laser Optics modify standard optics to custom sizes?

Yes, we can! We can also put a reflective coating on one of our plano-concave (or plano-convex) lenses.

Do you coat Customer Furnished Materials?

We have recently announced a new service to coat Customer Furnished Materials. Please see the link below for our press release. Any further questions should be directed to the contact information at the bottom of the press release.

The calibration date on my filter's spectral curve sheet expired. Do I need to recalibrate the filter?

No, the calibration date listed on the filter spectral curve sheets are the next calibration due date for the spectrometer on which the curve was measured. It has no effect on the filter's performance.

What is the difference between S- and P-polarization?

S-polarization (the s stems from the German word senkrecht meaning perpendicular) and P-polarization (the p means parallel) are the two main ways to describe two types of linearly polarized light. A primary misconception when using the terms is assuming that P is always vertical and S is always horizontal. This is not true. P and S are relative to a surface (usually the surface that the light is acting upon and/or reflecting from).

To properly define S- and P- polarizations, we first need to define the term plane of incidence. The plane of incidence is the plane that the incident and exiting beams lie in and is perpendicular to the surface that the light is incident upon.

P-polarization refers to light that is polarized parallel to the plane of incidence.

S-polarization refers to light that is polarized perpendicularly to the plane of incidence.

So saying that P-polarization is always up-down and S is always side-to-side is incorrect. One example where this is incorrect is with a common beamsplitter setup. In a beamsplitter being used where the entrance and exit beams are all parallel to the table top, P will be parallel to the table (side-to-side) and S will be perpendicular to the table (up-down).

The best thing is to keep in mind that S and P are relative to the plane of incidence.

What is the optical difference between N-BK7 and fused silica?

N-BK7 glass is one of the most common and widely used borosilicate crown glasses available. It performs well against most chemical tests, it is relatively hard, and does not scratch easily. N-BK7 glass can be handled without the need for special precautions. The bubble and inclusion content is also very low. N-BK7 has excellent transmission from 350nm to 1.5 µm. It can be a low-cost alternative to fused silica.

Fused silica is another common material used for optics. It has greater transmission than N-BK7 in the UV and IR spectrum. Transmission ranges from 180nm to 2 µm. Fused silica has a low coefficient of thermal expansion, providing stability and resistance to thermal shock over large temperature deviations. Fused silica has increased hardness and resistance to scratching. It can be an excellent alternative to N-BK7 glass, depending on the application.

What is the correct orientation for an Interference Filter?

A good rule of thumb, especially important if there is a risk of overheating or solarization, is that the interference filters should always be oriented with the shiniest (metallic) and most nearly colorless side toward the source in the radiant flux. This orientation will minimize the thermal load on the absorbing-glass blocking components. Reversing filter orientation will have no effect on filter transmittance near or within the passband.

Optical Coatings – Interference Filters (PDF).