Document and Entity Information - shares	6 Months Ended
	Mar. 31, 2020	May 04, 2020
Document And Entity Information [Abstract]
Entity Registrant Name	EMCORE CORP
Entity Central Index Key	0000808326
Document Type	10-Q
Document Period End Date	Mar. 31, 2020
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2020
Current Fiscal Year End Date	--09-30
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Amendment Flag	false
Entity Common Stock, Shares Outstanding		29,371,636
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes