5% CONVERTIBLE SENIOR SUBORDINATED NOTES DUE 2011

UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY TO THE COMPANY OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY (AND ANY PAYMENT HEREON IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL SINCE THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN. THIS NOTE IS A GLOBAL NOTE WITHIN THE MEANING OF THE INDENTURE HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITARY OR A NOMINEE THEREOF. THIS NOTE IS EXCHANGEABLE FOR SECURITIES REGISTERED IN THE NAME OF A PERSON OTHER THAN THE DEPOSITARY OR ITS NOMINEE ONLY IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE AND, UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR SECURITIES IN DEFINITIVE FORM, THIS NOTE MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITARY TO A NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE DEPOSITARY TO THE DEPOSITARY OR ANOTHER NOMINEE OF THE DEPOSITARY OR BY THE DEPOSITARY OR ANY SUCH NOMINEE TO A SUCCESSOR DEPOSITARY OR A NOMINEE OF SUCH SUCCESSOR DEPOSITARY AND TRANSFERS OF PORTIONS OF THIS GLOBAL NOTE SHALL BE LIMITED TO TRANSFERS MADE IN ACCORDANCE WITH SECTION 2.12 OF THE INDENTURE.

THIS NOTE (OR ITS PREDECESSOR) WAS ORIGINALLY ISSUED IN A TRANSACTION EXEMPT FROM REGISTRATION UNDER THE UNITED STATES SECURITIES ACT OF 1933 (THE “SECURITIES ACT”), AND THIS NOTE AND THE COMMON STOCK ISSUABLE UPON CONVERSION THEREOF MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR AN APPLICABLE EXEMPTION THEREFROM. EACH PURCHASER OF THIS NOTE IS HEREBY NOTIFIED THAT THE SELLER OF THIS NOTE MAY BE RELYING ON THE EXEMPTION FROM THE PROVISIONS OF SECTION 5 OF THE SECURITIES ACT PROVIDED BY RULE 144A THEREUNDER.

THE HOLDER OF THIS NOTE AGREES FOR THE BENEFIT OF THE COMPANY THAT (A) THIS NOTE AND THE NOTE COMMON STOCK ISSUABLE UPON CONVERSION THEREOF MAY BE OFFERED, RESOLD, PLEDGED OR OTHERWISE TRANSFERRED, ONLY (I) IN THE UNITED STATES TO A PERSON WHOM THE SELLER REASONABLY BELIEVES IS A QUALIFIED INSTITUTIONAL BUYER (AS DEFINED IN RULE 144A UNDER THE SECURITIES ACT) IN A TRANSACTION MEETING THE REQUIREMENTS OF RULE 144A, (II) OUTSIDE THE UNITED STATES IN AN OFFSHORE TRANSACTION IN ACCORDANCE WITH RULE 904 UNDER THE SECURITIES ACT, (III) PURSUANT TO AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT PROVIDED BY RULE 144 THEREUNDER (IF AVAILABLE) OR (IV) PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT, IN EACH OF CASES (I) THROUGH (IV) IN ACCORDANCE WITH ANY APPLICABLE SECURITIES LAWS OF ANY STATE OF THE UNITED STATES, AND (B) THE HOLDER WILL, AND EACH SUBSEQUENT HOLDER IS REQUIRED TO, NOTIFY ANY PURCHASER OF THIS NOTE FROM IT OF THE RESALE RESTRICTIONS REFERRED TO IN (A) ABOVE. IN ANY CASE, THE HOLDER HEREOF WILL NOT, DIRECTLY OR INDIRECTLY, ENGAGE IN ANY HEDGING TRANSACTIONS WITH REGARD TO THE NOTES EXCEPT AS PERMITTED UNDER THE SECURITIES ACT.

EMCORE Corporation, a New Jersey corporation (the “Company”, which term shall include any successor corporation under the Indenture referred to on the reverse hereof), promises to pay to Cede & Co., or registered assigns, the principal sum of sixteen million five hundred eighty thousand four hundred and sixty Dollars ($16,580,460) on May 15, 2011 or such greater or lesser amount as is indicated on the Schedule of Exchanges of Notes on the other side of this Note.

Interest Payment Dates: May 15 and November 15

Record Dates: May 1 and November 1

This Note is convertible as specified on the other side of this Note. Additional provisions of this Note are set forth on the other side of this Note.

IN WITNESS WHEREOF, the Company has caused this instrument to be duly executed.

EMCORE Corporation

By: /s/ Howard W. Brodie   

Howard W. Brodie

Executive Vice President and Chief Legal Officer

Attest:

By: /s/ Ian T. Graham  

Ian T. Graham

Assistant Secretary

Dated:  November 16, 2005

Trustee’s Certificate of Authentication: This is one of the Notes referred to in the within-mentioned Indenture.

DEUTSCHE BANK TRUST COMPANY AMERICAS,

as Trustee

By:  /s/ Wanda Camacho   

EMCORE Corporation, a New Jersey corporation (the “Company,” which term shall include any successor corporation under the Indenture hereinafter referred to), promises to pay interest on the principal amount of this Note at the rate of 5% per annum. The Company shall pay interest semiannually on May 15 and November 15 of each year, commencing May 15, 2006, unless such date is not a business day, in which case, we shall pay interest on the next succeeding business day and such payment shall be deemed to have been paid on such interest payment date and no interest shall accrue during the additional period of time. Interest on the Notes shall accrue from the most recent date to which interest has been paid or, if no interest has been paid, from November 16, 2005; provided, however, that if there is not an existing default in the payment of interest and if this Note is authenticated between a record date referred to on the face hereof and the next succeeding interest payment date, interest shall accrue from such interest payment date. Interest will be computed on the basis of a 360-day year of twelve 30-day months.

The Company shall pay interest on this Note (except defaulted interest) to the person who is the Holder of this Note at the close of business on May 1 or November 1, as the case may be, next preceding the related interest payment date. The Holder must surrender this Note to a Paying Agent to collect payment of principal. The Company will pay principal and interest in money of the United States that at the time of payment is legal tender for payment of public and private debts. The Company may, however, pay principal and interest in respect of any Definitive Note by check or wire payable in such money; provided, however, that a Holder with an aggregate principal amount in excess of $2,000,000 will be paid by wire transfer in immediately available funds at the election of such Holder. The Company may mail an interest check to the Holder’s registered address. Notwithstanding the foregoing, so long as this Note is registered in the name of a Depositary or its nominee, all payments hereon shall be made by wire transfer of immediately available funds to the account of the Depositary or its nominee.

Initially, Deutsche Bank Trust Company Americas (the “Trustee,” which term shall include any successor trustee under the Indenture hereinafter referred to) will act as Paying Agent, Registrar and Conversion Agent. The Company may change any Paying Agent, Registrar or Conversion Agent without notice to the Holder. The Company or any of its Subsidiaries may, subject to certain limitations set forth in the Indenture, act as Paying Agent or Registrar.

This Note is one of a duly authorized issue of Notes of the Company designated as its 5% Convertible Senior Subordinated Notes due 2011 (the “Notes”), issued under an Indenture dated as of November 16, 2005 (together with any supplemental indentures thereto, the “Indenture”), between the Company and the Trustee. The terms of this Note include those stated in the Indenture and those required by or made part of the Indenture by reference to the Trust Indenture Act of 1939, as amended, as in effect on the date of the Indenture. This Note is subject to all such terms, and the Holder of this Note is referred to the Indenture and said Act for a statement of them. All capitalized terms used but not defined herein shall have the meaning ascribed to such term in the Indenture.

The Notes are subordinated unsecured obligations of the Company. The aggregate principal amount of Notes which may be authenticated and delivered pursuant to the Indenture is unlimited. The Indenture does not limit other debt of the Company, secured or unsecured, including Senior Indebtedness.

The Notes may be redeemed at the election of the Company, as a whole or in part from time to time, at any time (a “ Provisional Redemption ”), upon at least 20 and not more than 60 days’ notice by mail to the Holders of the Notes (a “ Provisional Redemption Notice ”) at a redemption price equal to $1,000 per $1,000 principal amount of the Notes redeemed plus accrued and unpaid interest, if any (such amount, together with the Early Call Premium described below, the “ Provisional Redemption Price ”), to but excluding the date of redemption (the “ Provisional Redemption Date ”) if the Closing Sale Price of the Common Stock has exceeded 150% of the Conversion Price for at least 20 Trading Days within a period of any 30 consecutive Trading Days ending on the Trading Day prior to the date of mailing of the notice of Provisional Redemption (the “ Provisional Redemption Notice Date ”).

Except as set forth above, the Company shall not have the option to redeem the Notes.

If the Company delivers a Provisional Redemption Notice on or prior to May 15, 2007, the Company shall make an additional payment, at its option, in cash or Common Stock or a combination of cash and Common Stock (the “ Early Call Premium ”) with respect to the Notes called for redemption to holders on the Provisional Redemption Notice Date in an amount equal to $150.00 per $1,000 principal amount of the Notes, less the amount of any interest actually paid (including, if the Provisional Redemption Date occurs after a record date but before an interest payment date, any interest paid or to be paid in connection with such interest payment date) on such Notes prior to the Provisional Redemption Date. Payments made in Common Stock will be valued at 95% of the average closing sales prices of Common Stock for the five Trading Days ending on the third day prior to the Prov