Optica Citation Style: A Complete Guide
Optica Publishing Group (formerly the Optical Society of America, OSA) defines the citation style used across its flagship journals — Optica, Optics Letters, Optics Express, and others. It uses square-bracket numbers in the text and a numbered reference list ordered by first appearance, a clean system built for the fast-moving literature of optics and photonics.
What is Optica citation style?
Optica Publishing Group (OPG) is the successor organization to the Optical Society of America (OSA), rebranded in 2021. Its journals — including Optica, Optics Letters, Optics Express, Applied Optics, and Journal of the Optical Society of America A & B — all follow the same reference style defined in the OPG author guidelines.
Like ACS and AMA, Optica style uses a numbered citation system: references are assigned numbers in the order they first appear in the text, and those numbers are reused on every subsequent mention of the same source. The matching reference list is ordered numerically, not alphabetically.
Optica style differs from ACS and AMA in several important ways: in-text numbers appear in square brackets (not superscripts), author names are given as initials followed by last name (e.g., J. Smith rather than Smith J), and the article title is always included in journal references. Journal names are abbreviated but not italicized.
In-text citations
Optica in-text citations are Arabic numerals inside square brackets, placed directly in the running text. They typically appear before the period at the end of a sentence — unlike AMA superscripts, which go after the period.
Numbers are assigned in order of first appearance. Once a source has a number, that same number is reused on every subsequent citation of the same work. When citing multiple sources together, list their numbers separated by commas inside one pair of brackets. For a consecutive range, use an en dash.
Single-mode fiber lasers are now routinely operated at kilowatt output powers [1].
Several groups have demonstrated coherent beam combining in this regime [2,3,5].
Early work on nonlinear pulse compression established the theoretical framework [4–7].
Citing in the flow of text
When a citation naturally fits mid-sentence — for example, when referring to an author by name — the bracket follows the author reference directly.
As shown by Yariv and Yeh [8], coupled-mode theory accurately predicts the spectral response of fiber Bragg gratings.
Reference list rules
The reference list appears at the end of the manuscript under the heading References. Each entry is numbered to match its bracket in the text and listed in citation order — not alphabetically.
Author names
Author names in Optica references follow the format: Initials Last Name — for example, J. A. Smith. Periods follow each initial, and a space separates initials from the last name. Multiple authors are separated by commas. If there are more than six authors, list the first author and add "et al." — Optica journals apply a strict et al. threshold that differs by publication, so always check the specific journal's author guidelines.
One author: J. A. Smith
Three authors: J. A. Smith, B. C. Jones, and D. E. Williams
Many authors: J. A. Smith, B. C. Jones, D. E. Williams, et al.
Journal name abbreviations
Journal titles are abbreviated in Optica references following standard abbreviation lists (such as the CAS Source Index or ISSN portal). Abbreviated journal names are not italicized in Optica style. The volume number is bold, and the issue number (if included) appears in parentheses after the volume.
- Optics Letters becomes Opt. Lett.
- Optics Express becomes Opt. Express
- Applied Optics becomes Appl. Opt.
- Journal of the Optical Society of America A becomes J. Opt. Soc. Am. A
- Nature Photonics becomes Nat. Photonics
- Physical Review Letters becomes Phys. Rev. Lett.
DOIs and URLs
When a DOI is available, include it at the end of the reference as a full
hyperlink: https://doi.org/10.xxxx/yyyyy. If no DOI exists,
include the full URL. Optica journals strongly encourage DOI inclusion for
all published sources.
Journal articles
Journal articles are the dominant source type in optics literature. The Optica format is:
A. Author, B. Author, and C. Author, "Article title," Abbrev. J. Name Vol(Issue), first–last page (Year).
Note that the article title is enclosed in quotation marks, the journal name is abbreviated but not italicized, the volume number is in bold, and the year appears at the end in parentheses. This year-at-end format distinguishes Optica style from ACS and AMA, where the year appears earlier in the reference.
1. D. J. Richardson, J. M. Fini, and L. E. Nelson, "Space-division multiplexing in optical fibres," Nat. Photonics 7(5), 354–362 (2013). https://doi.org/10.1038/nphoton.2013.94
2. F. Poletti and P. Horak, "Description of ultrashort pulse propagation in multimode optical fibers," J. Opt. Soc. Am. B 25(10), 1645–1654 (2008). https://doi.org/10.1364/JOSAB.25.001645
3. Y. Liu, J. Zhao, and W. Li, "Integrated photonic neural network accelerator," Optica 10(3), 034001 (2023). https://doi.org/10.1364/OPTICA.10.034001
Online-ahead-of-print articles
For articles accepted but not yet assigned to a volume and issue, omit the volume/issue/page information and include only the DOI or URL along with a note that it is published online.
4. M. Chen, R. Patel, and S. Yamamoto, "Adaptive wavefront correction using deep learning," Opt. Lett., early access (2026). https://doi.org/10.1364/OL.2026.500001
Books and book chapters
Entire book
For a book, list the author(s), the book title in italics, the edition if not the first, the publisher, and the year.
A. Author and B. Author, Book Title, Nth ed. (Publisher, Year).
5. A. Yariv and P. Yeh, Photonics: Optical Electronics in Modern Communications, 6th ed. (Oxford University Press, 2007).
6. G. P. Agrawal, Nonlinear Fiber Optics, 6th ed. (Academic Press, 2019).
Chapter in an edited book
When citing a specific chapter, name the chapter author(s) first, then the chapter title in quotation marks, then introduce the book with "in" (lowercase) followed by the book title in italics, the editor(s), the publisher, the year, and the chapter page range.
A. Author, "Chapter title," in Book Title, B. Editor, ed. (Publisher, Year), pp. xx–xx.
7. J. W. Goodman, "Coherence of optical waves," in Statistical Optics, J. W. Goodman, ed. (Wiley, 2015), pp. 157–198.
Websites and online sources
For web pages, datasheets, and other online documents that are not formally published journals or books, Optica style requires the author or organization, the title of the page or document in quotation marks, the website or publisher name, and the URL with an access date.
Organization or Author, "Title of web page," Website Name (Year), retrieved Month DD, Year, URL.
8. Thorlabs, "Single Mode Patch Cable, 780 nm, FC/APC," Thorlabs Product Catalog (2024), retrieved April 15, 2026, https://www.thorlabs.com/thorproduct.cfm?partnumber=P1-780A-FC-2
9. International Telecommunication Union, "Characteristics of a Single-Mode Optical Fibre and Cable," ITU-T G.652 (2016), retrieved April 15, 2026, https://www.itu.int/rec/T-REC-G.652
Conference papers and proceedings
Conference papers are extremely common in optics research. CLEO, OFC, SPIE, and Frontiers in Optics are among the most-cited venues. The format for a conference paper is:
A. Author and B. Author, "Paper title," in Conference Name, OSA/OPG Technical Digest (Publisher, Year), paper CodeXX.
10. T. Eidam, S. Hanf, E. Seise, T. V. Andersen, T. Gabler, C. Wirth, T. Schreiber, J. Limpert, and A. Tünnermann, "Femtosecond fiber CPA system emitting 830 W average output power," in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optica Publishing Group, 2010), paper CThA1.
11. M. J. F. Digonnet and H. J. Shaw, "Analysis of a tunable single mode optical fiber coupler," Proc. SPIE 326, 152–160 (1982). https://doi.org/10.1117/12.933287
For SPIE proceedings, the format resembles a journal article: use "Proc. SPIE" as the abbreviated journal name with the volume number in bold, followed by the page range and year.
Theses and dissertations
Graduate theses are cited with the author, title in quotation marks, the degree type, the institution, and the year.
A. Author, "Thesis title," Ph.D. dissertation (or M.S. thesis), University Name (Year).
12. R. T. Schermer, "Improved scalability of single-transverse-mode optical fiber," Ph.D. dissertation, University of Michigan (2004).
Common mistakes to avoid
Using superscripts instead of square brackets
Optica style uses [1], [2,3], [4–6] in the text — not superscript numbers. Writers familiar with AMA or Nature journals sometimes default to superscripts, which is incorrect for OPG journals.
Putting the year in the wrong position
In Optica journal references, the year goes at the end in
parentheses, after the page range: 354–362 (2013). Writers
accustomed to ACS or AMA style, where the year follows the journal name,
often place it too early.
Forgetting to bold the volume number
The journal volume number is typeset in bold in Optica references — 7(5), 354–362. Omitting the bold formatting is a common oversight, especially when typing references manually.
Alphabetizing the reference list
Like ACS and AMA, Optica references are ordered by citation number — the order sources first appear in the text. Alphabetizing is a mistake carried over from APA or MLA habits.
Italicizing the journal name
Abbreviated journal names in Optica references are not italicized. The book title, on the other hand, is italicized. Getting these mixed up is a common source of formatting errors.
Missing the article title
Unlike ACS style (which omits article titles), Optica references always include the article title in quotation marks. Leaving it out produces an incomplete reference.
Quick summary
| Feature | Optica Rule |
|---|---|
| In-text format | Square-bracket numbers — [1], [2,3], [4–6] |
| Numbering | Sequential by order of first appearance in the text |
| Reference list order | Numbered order — not alphabetical |
| Author format | Initials then last name — e.g., J. A. Smith (periods after initials) |
| Article title | Always included, enclosed in quotation marks |
| Journal names | Abbreviated, not italicized |
| Volume number | Bold — e.g., 7(5) |
| Year position | At the end of the entry, in parentheses after the page range |
| DOI | Full https://doi.org/... URL when available |
| Conference papers | Cited with paper code; SPIE formatted like a journal article |
Optica style is built for precision and rapid reading in a field where practitioners regularly scan dozens of references at a glance. Its square-bracket numbers keep the text uncluttered, the bold volume number makes entries scannable, and the year-at-end convention immediately signals the recency of each source. Once you learn the author format, the bold volume, and the year placement, formatting correct Optica references becomes second nature.
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