About Photonica

Photonica is a free reference for photonics engineering: the definitions, measurement procedures, material data, and calculations needed at the bench, written to be checked rather than taken on faith.

Why this exists

Photonics has a thin reference layer. Textbooks derive the equation and stop before the measurement. Papers report the number and omit the procedure that produced it. Vendor application notes are frequently excellent and always have something to sell. Between those sits the layer this site is trying to fill: free, sourced, and written at the level of somebody actually running the measurement.

The field is not oversupplied with encyclopedias. For general photonics terminology, the RP Photonics Encyclopedia has been the standing reference for two decades and is still the best starting point for most terms. There is room next to it, particularly on the characterization side: the step-by-step of extracting a threshold current, the failure modes that quietly make a linewidth measurement wrong, the numbers a specification actually needs alongside the conditions they were measured under. Those are the questions that send engineers into forum threads and course PDFs. They should have a citable page instead.

What is here

Counts below are generated at build time from the published files, so they cannot drift away from what the site actually contains.

• 262 glossary entries covering terms, parameters, and their definitional pitfalls
• 25 long-form articles on measurement procedure, component comparison, and parameter extraction
• 6 material pages with optical constants and the wavelength ranges they hold over
• 7 calculators that run in the browser, with the governing equation shown next to the result

Roughly 174,000 words in total, cross-linked so that a term used in a procedure resolves to its own definition rather than assuming you already have it.

How entries are written

Four standards apply to everything published here, so you know what you are reading:

• Sourced or marked as typical. Values taken from published measurements are attributed where they appear: book, standard, paper, or application note, by name. Values that are typical of a device class rather than from one specific source are given as a labeled range, never dressed up as an exact figure.
• Bench first. Where a procedure has a gap between how it is described in the literature and how it goes in a real setup, the entry documents the real setup, including the failure modes that produce a plausible but wrong answer.
• No paid placement. Instruments, vendors, and part numbers appear when the procedure depends on instrument-specific behavior, and for no other reason. Nothing on this site is sponsored, and no one can buy a mention.
• Dated and corrected in public. Entries carry their publication date and any revision date. Substantive corrections are noted on the page rather than silently swapped in, so a reader who saved a number can tell whether it changed.

Independence

Photonica is independent. It is not affiliated with and does not speak for any employer, university, standards body, or manufacturer. There is no advertising, no sponsored content, and no affiliate arrangement of any kind. The site carries no tracking cookies and sits behind no paywall or registration wall. How it is built, hosted, and measured is documented in the colophon.

Licensing

All written content is published under CC BY 4.0. Use it, adapt it, teach from it. Credit Photonica with a link back. Open licensing is deliberate: work that can be copied, checked, and corrected by anyone is work that has to hold up.

Corrections

Errors get fixed, and corrections are welcome from anyone. Reports that include the page URL and a checkable source, meaning a datasheet page, a textbook section, or a paper, get handled fastest. Write to hello@photonica.io or see the contact page.