应用光电美股招股说明书(2026-03-12版)

AMENDMENT NO. 1 dated March12, 2026TO PROSPECTUS SUPPLEMENT dated February26, 2026(To Prospectus dated December18, 2024) Applied Optoelectronics, Inc.Common Stock This Amendment No. 1 to prospectus supplement, or this amendment, amends our prospectus supplement datedFebruary26, 2026 (the “prospectus supplement”). This amendment should be read in conjunction with the prospectussupplement and the prospectus dated December18, 2024, both of which are to be delivered with this amendment. Thisamendment only amends those sections of the prospectus supplement listed in this amendment; all other sections of the On February26, 2026, we have entered into an Equity Distribution Agreement with Raymond James & Associates,Inc. (“Raymond James”) and Needham & Company, LLC (“Needham”), or the sales agreement, relating to shares of ourcommon stock offered by the prospectus supplement. On March12, 2026, we amended the sales agreement to increasethe total amount of common stock that we may offer and sell under the sales agreement from $250,000,000 to$500,000,000 (which amount includes what we have already sold pursuant to the sales agreement prior to the date of thisamendment) from time to time through Raymond James and Needham, acting as agents (each, an “Agent” and Our common stock is listed on The Nasdaq Global Market under the symbol “AAOI.” On March11, 2026, the lastreported sale price of our common stock on The Nasdaq Global Market was $127.01 per share. Sales of our common stock, if any, under this prospectus supplement, as amended by this amendment, may bemade in sales deemed to be “at-the-market” equity offerings as defined in Rule415 promulgated under the SecuritiesAct of 1933, as amended, or the Securities Act, including sales made directly on or through The Nasdaq Global Market,the existing trading market for our common stock, sales made to or through a market maker other than on an exchangeor otherwise, in negotiated transactions at market prices prevailing at the time of sale or at prices related to suchprevailing market prices, and any other method permitted by law, including in privately negotiated transactions. TheAgents are not required to sell any specific number or dollar amount of securities, but will act as sales agents and use Except as otherwise described in the sales agreement, the Agents will be entitled to compensation at a commissionrate of up to 2.0% of the gross sales price per share sold. In connection with the sale of our common stock on our behalf,the Agents may be deemed to be “underwriters” within the meaning of the Securities Act and the compensation of theAgents may be deemed to be underwriting commissions or discounts. We have also agreed to provide indemnification INVESTING IN OUR SECURITIES INVOLVES SIGNIFICANT RISKS. YOU SHOULD REVIEW CAREFULLY THE“RISK FACTORS” BEGINNING ON PAGES-3OF THIS AMENDMENT AND UNDER SIMILAR HEADINGS INTHE OTHER DOCUMENTS THAT ARE INCORPORATED BY REFERENCE INTO THIS PROSPECTUS Neither the Securities and Exchange Commission nor any state securities commission has approved or disapprovedof these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is acriminal offense. RAYMOND JAMES NEEDHAM & COMPANY The date of this amendment to prospectus supplement is March12, 2026. ABOUT THIS AMENDMENT TO PROSPECTUS SUPPLEMENT This amendment is part of a registration statement that wefiled with the Securities and ExchangeCommission, or the SEC, using a “shelf” registration process. Under this amendment, the prospectussupplement, and the accompanying base prospectus, we may offer shares of our common stock having We provide information to you about this offering of shares of our common stock in three separatedocuments that are bound together: (1)this amendment, (2)the prospectus supplement, whichtogether with the amendment describe the specific details regarding this offering; and (3)theaccompanying base prospectus, which provides general information, some of which may not apply tothis offering. If information in this amendment is inconsistent with the accompanying prospectussupplement or the accompanying base prospectus, you should rely on this amendment. However, if To the extent there is a conflict between the information contained in this amendment, on the onehand, and the information contained in the prospectus supplement and the accompanying baseprospectus or in any document incorporated by reference in the prospectus supplement having anearlier date than the date of this amendment, on the other hand, you should rely on the information in In making your investment decision, you should rely only on the information contained in thisamendment, or contained in the prospectus supplement or incorporated by reference in the prospectussupplement, in the accompanying base prospectus and in any free writing prospectus with respect tothis offeringfiled by us with the SEC. We have not, and the Agents have not, auth