Document and Entity Information - shares	3 Months Ended
	Dec. 31, 2018	Jan. 31, 2019
Document And Entity Information [Abstract]
Entity Registrant Name	EMCORE CORP
Entity Central Index Key	0000808326
Document Type	10-Q
Document Period End Date	Dec. 31, 2018
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2019
Current Fiscal Year End Date	--09-30
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Amendment Flag	false
Entity Common Stock, Shares Outstanding		27,670,466