Intangible Assets and Goodwill - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Finite-Lived Intangible Assets [Line Items]
Carrying amount	$ 21,591	$ 14,251
Fair value and impairment expense	2,125	0
Goodwill	0	17,894	$ 69
Additions from acquisition	1,150	17,825
In Process Research and Development
Finite-Lived Intangible Assets [Line Items]
Intangible assets acquired		6,700
Trademarks
Finite-Lived Intangible Assets [Line Items]
Intangible assets acquired	900	2,200
S & N and Emcore Chicago Acquisitions
Finite-Lived Intangible Assets [Line Items]
Adjustments to preliminary purchase price allocation	1,200
Expected tax deductible amount of goodwill	$ 0
Patents
Finite-Lived Intangible Assets [Line Items]
Intangible assets useful life (in years)	7 years
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Carrying amount	$ 4,690	3,260
Intangible assets useful life (in years)	8 years
Technology
Finite-Lived Intangible Assets [Line Items]
Carrying amount	$ 16,901	$ 10,991
Trademarks
Finite-Lived Intangible Assets [Line Items]
Carrying amount	2,200
Impairment expense	19,000
In Process Research and Development
Finite-Lived Intangible Assets [Line Items]
Carrying amount	800
Fair value and impairment expense	$ 1,300
Intangible assets useful life (in years)	8 years
Minimum | Technology
Finite-Lived Intangible Assets [Line Items]
Intangible assets useful life (in years)	2 years
Maximum | Technology
Finite-Lived Intangible Assets [Line Items]
Intangible assets useful life (in years)	8 years