Acquisitions - Pro Forma Information (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Business Acquisition [Line Items]
Revenue	$ 26,820	$ 32,650	$ 51,773	$ 74,886
Cost of revenue	23,109	23,633	45,003	50,072
Gross profit	3,711	9,017	6,770	24,814
Operating expense:
Selling, general, and administrative	9,951	7,563	19,895	14,750
Research and development	5,797	4,535	11,148	9,162
Severance	(17)	20	458	1,318
(Gain) loss on sale of assets	24	(788)	(1,147)	(601)
Total operating expense	15,755	11,330	30,354	24,629
Operating (loss) income	(12,044)	(2,313)	(23,584)	185
Other (expense) income:
Interest expense, net	(222)	(12)	(463)	(23)
Foreign exchange gain	46	(17)	121	25
Other income	46	0	153	0
Total other (expense) income	(130)	(29)	(189)	2
(Loss) income before income tax (expense) benefit	(12,174)	(2,342)	(23,773)	187
Income tax (expense) benefit	(54)	117	(148)	2
Net (loss) income		(2,225)	(23,921)	189
Foreign exchange translation adjustment	8	2	55	22
Comprehensive (loss) income	$ (12,220)	$ (2,223)	$ (23,866)	$ 211
Net loss per basic share (in dollars per share)	$ (0.27)	$ (0.06)	$ (0.58)	$ 0.01
Weighted-average number of basic shares outstanding (in shares)	45,240	37,217	41,356	37,082
Net (loss) income per diluted share (in dollars per share)	$ (0.27)	$ (0.06)	$ (0.58)	$ 0.01
Weighted-average number of diluted shares outstanding (in shares)	45,240	37,217	41,356	38,384
Pro Forma
Business Acquisition [Line Items]
Revenue		$ 40,348		$ 90,282
Cost of revenue		29,631		62,069
Gross profit		10,717		28,213
Operating expense:
Selling, general, and administrative		9,442		18,288
Research and development		5,714		11,520
Severance		20		1,318
(Gain) loss on sale of assets		(788)		(601)
Total operating expense		14,388		30,525
Operating (loss) income		(3,671)		(2,312)
Other (expense) income:
Interest expense, net		306		613
Foreign exchange gain		(17)		25
Other income		34		68
Total other (expense) income		323		706
(Loss) income before income tax (expense) benefit		(3,348)		(1,606)
Income tax (expense) benefit		98		(34)
Net (loss) income		(3,250)		(1,640)
Foreign exchange translation adjustment		2		22
Comprehensive (loss) income		$ (3,248)		$ (1,618)
Net loss per basic share (in dollars per share)		$ (0.09)		$ (0.04)
Weighted-average number of basic shares outstanding (in shares)		37,217		37,082
Net (loss) income per diluted share (in dollars per share)		$ (0.09)		$ (0.04)
Weighted-average number of diluted shares outstanding (in shares)		37,217		38,384
Pro Forma | Pro Forma Adjustments
Business Acquisition [Line Items]
Revenue		$ 0		$ 0
Cost of revenue		171		342
Gross profit		(171)		(342)
Operating expense:
Selling, general, and administrative		(1,026)		(2,051)
Research and development		(264)		(529)
Severance		0		0
(Gain) loss on sale of assets		0		0
Total operating expense		(1,290)		(2,580)
Operating (loss) income		1,119		2,238
Other (expense) income:
Interest expense, net		318		636
Foreign exchange gain		0		0
Other income		0		0
Total other (expense) income		318		636
(Loss) income before income tax (expense) benefit		1,437		2,874
Income tax (expense) benefit		(6)		(11)
Net (loss) income		1,431		2,863
Foreign exchange translation adjustment		0		0
Comprehensive (loss) income		$ 1,431		$ 2,863
Net loss per basic share (in dollars per share)		$ 0		$ 0
Weighted-average number of basic shares outstanding (in shares)		0		0
Net (loss) income per diluted share (in dollars per share)		$ 0		$ 0
Weighted-average number of diluted shares outstanding (in shares)		0		0
Pro Forma | EMCORE Corporation (excluding EMCORE Chicago)
Business Acquisition [Line Items]
Revenue		$ 32,650		$ 74,886
Cost of revenue		23,633		50,072
Gross profit		9,017		24,814
Operating expense:
Selling, general, and administrative		7,563		14,750
Research and development		4,535		9,162
Severance		20		1,318
(Gain) loss on sale of assets		(788)		(601)
Total operating expense		11,330		24,629
Operating (loss) income		(2,313)		185
Other (expense) income:
Interest expense, net		(12)		(23)
Foreign exchange gain		(17)		25
Other income		0		0
Total other (expense) income		(29)		2
(Loss) income before income tax (expense) benefit		(2,342)		187
Income tax (expense) benefit		117		2
Net (loss) income		(2,225)		189
Foreign exchange translation adjustment		2		22
Comprehensive (loss) income		$ (2,223)		$ 211
Net loss per basic share (in dollars per share)		$ 0.06		$ 0.01
Weighted-average number of basic shares outstanding (in shares)		37,217		37,082
Net (loss) income per diluted share (in dollars per share)		$ 0.06		$ 0.01
Weighted-average number of diluted shares outstanding (in shares)		37,217		38,384
Pro Forma | EMCORE Chicago
Business Acquisition [Line Items]
Revenue		$ 7,698		$ 15,396
Cost of revenue		5,827		11,655
Gross profit		1,871		3,741
Operating expense:
Selling, general, and administrative		2,905		5,589
Research and development		1,443		2,887
Severance		0		0
(Gain) loss on sale of assets		0		0
Total operating expense		4,348		8,476
Operating (loss) income		(2,477)		(4,735)
Other (expense) income:
Interest expense, net		0		0
Foreign exchange gain		0		0
Other income		34		68
Total other (expense) income		34		68
(Loss) income before income tax (expense) benefit		(2,443)		(4,667)
Income tax (expense) benefit		(13)		(25)
Net (loss) income		(2,456)		(4,692)
Foreign exchange translation adjustment		0		0
Comprehensive (loss) income		$ (2,456)		$ (4,692)