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