Cover - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Dec. 09, 2023	Mar. 31, 2023
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Sep. 30, 2023
Current Fiscal Year End Date	--09-30
Document Transition Report	false
Entity File Number	001-36632
Entity Registrant Name	EMCORE Corporation
Entity Incorporation, State or Country Code	NJ
Entity Tax Identification Number	22-2746503
Entity Address, Address Line One	2015 W. Chestnut Street
Entity Address, City or Town	Alhambra
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	91803
City Area Code	626
Local Phone Number	293-3400
Title of 12(b) Security	Common stock, no par value
Trading Symbol	EMKR
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 60.9
Entity Common Stock, Shares Outstanding		77,172,167
Documents Incorporated by Reference	In accordance with General Instruction G(3) of Form 10-K, certain information required by Part III hereof will either be incorporated into this Annual Report on Form 10-K by reference to the Definitive Proxy Statement for the Annual Meeting of Shareholders filed within 120 days of the fiscal year ended September 30, 2023 (the “2024 Proxy Statement”), or will be included in an amendment to this Annual Report on Form 10-K filed within 120 days of September 30, 2023.
Entity Central Index Key	0000808326
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2023
Amendment Flag	false