Document and Entity Information - shares	9 Months Ended
	Jun. 30, 2020	Aug. 03, 2020
Document And Entity Information [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
Document Transition Report	false
Entity File Number	001-36632
Entity Registrant Name	EMCORE CORP
Entity Incorporation, State or Country Code	NJ
Entity Tax Identification Number	22-2746503
Entity Address, Address Line One	New Jersey
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
Trading Symbol	EMKR
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		29,408,087
Entity Central Index Key	0000808326
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2020
Current Fiscal Year End Date	--09-30
Amendment Flag	false