Exhibit 4.1



AO APPLIED   OPTOELECTRONICS, INC. INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE   SEE REVERSE SIDE FOR CERTAIN DEFINITIONS FULLY PAID AND NON-ASSESSABLE COMMON   SHARES, $0.001 PAR VALUE, OF APPLIED OPTOELECTRONICS, INC. transferable on   the books of the Corporation byCthe hOolder Mhereof iMn persoOn or bNy   Attorney upon surrender of this certificate properly endorsed. This   certificate is not valid until countersigned and registered by the Transfer   Agent and Registrar. IN WITNESS WHEREOF, the said Corporation has caused this   certificate to be signed by facsimile signatures of its duly authorized   officers. Dated: SEAL 2013 ★ PRESIDENT AND CEO GENERAL COUNSEL AND   SECRETARY AMERICAN FINANCIAL PRINTING INCORPORATED – MINNEAPOLIS L O   COUNTERSIGNED AND REGISTERED: CONTINENTAL STOCK TRANSFER & TRUST COMPANY   TRANSFER AGENT AND REGISTRAR BY AUTHORIZED SIGNATURE P THIS CERTIFIES THAT is   the owner of CUSIP 03823U 10 2 


    




 









 



This   Certificate and the shares represented hereby are issued and shall have the   rights specified in and be held subject to all of the provisions of the   Articles of Incorporation and the Bylaws of said Corporation and any   amendments and restatements thereof, to all of which the holder of this   Certificate, by acceptance hereof, assents and agrees to be bound. A   statement of the rights, preferences, privileges and restrictions granted to   or imposed upon the respective classes or series of the Corporation’s capital   stock and upon the holders thereof as established by said Articles of   Incorporation and Bylaws and a statement of the number of shares constituting   each class or series of stock and the designation thereof, may be obtained by   any shareholder, upon request and without charge, at the principal office of   the Corporation. The following abbreviations, when used in the inscription on   the face of this certificate, shall be construed as though they were written   out in full according to applicable laws or regulations: UTMA – Custodian TEN   COM TEN ENT JT TEN – as tenants in common – as tenants by entireties – as   joint tenants with right of survivorship and not as tenants in common (Cust)   (Minor) under Uniform Transfers to Minors Act (State) Additional abbreviations   may also be used though not in above list. For value received hereby sell,   assign, and transfer unto PLEASE INSERT SOCIAL SECURITY OR OTHER IDENTIFYING   NUMBER OF ASSIGNEE (PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS INCLUDING ZIP   CODE OF ASSIGNEE) Shares of the capital stock represented by the within   Certificate, and do hereby irrevocably constitute and appoint Attorney to   transfer the said stock on the books of the within-named Corporation with   full power of substitution in the premises. Dated X X NOTICE: THE SIGNATURE   TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME AS WRITTEN UPON THE FACE OF   THE CERTIFICATE IN EVERY PARTICULAR WITHOUT ALTERATION OR ENLARGEMENT OR ANY   CHANGE WHATEVER. SIGNATURE GUARANTEED ALL GUARANTEES MUST BE MADE BY A   FINANCIAL INSTITUTION (SUCH AS A BANK OR BROKER) WHICH IS A PARTICIPANT IN   THE SECURITIES TRANSFER AGENTS MEDALLION PROGRAM (“STAMP”), THE NEW YORK   STOCK EXCHANGE, INC. MEDALLION SIGNATURE PROGRAM (“MSP”), OR THE STOCK   EXCHANGES MEDALLION PROGRAM (“SEMP”) AND MUST NOT BE DATED. GUARANTEES BY A   NOTARY PUBLIC ARE NOT ACCEPTABLE.