CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (16,368,000)	$ (21,505,000)	$ (10,337,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Allowance for doubtful accounts and other	(39,000)	35,000	(17,000)
Provision for excess and obsolete inventories	402,000	466,000	343,000
Non-cash lease expense	373,000	598,000	611,000
Depreciation and amortization	1,004,000	1,214,000	1,434,000
Stock-based compensation	2,993,000	2,854,000	2,566,000
Amortization of premium on investments	69,000	88,000
Changes in assets and liabilities:
Accounts receivable	(814,000)	2,630,000	1,026,000
Inventories	(714,000)	(527,000)	1,060,000
Prepaid expenses and other assets	(70,000)	440,000	(431,000)
Accounts payable	(127,000)	383,000	(680,000)
Accrued expenses and other liabilities	(535,000)	(1,928,000)	(256,000)
Net cash used in operating activities	(13,826,000)	(15,252,000)	(4,681,000)
Cash flows from investing activities:
Purchase of investments	(7,163,000)	(17,510,000)	(18,116,000)
Maturities of short-term investments	12,132,000	21,000,000	27,418,000
Decrease in MikaMonu escrow deposit			1,000,000
Purchases of property and equipment	(774,000)	(203,000)	(331,000)
Net cash provided by investing activities	4,195,000	3,287,000	9,971,000
Cash flows from financing activities:
Payment of MikaMonu escrow deposit			(428,000)
Proceeds from issuance of common stock under employee stock plans	2,368,000	4,693,000	4,149,000
Net cash provided by financing activities	2,368,000	4,693,000	3,721,000
Net increase (decrease) in cash and cash equivalents	(7,263,000)	(7,272,000)	9,011,000
Cash and cash equivalents at beginning of the period	44,234,000	51,506,000	42,495,000
Cash and cash equivalents at end of the period	36,971,000	44,234,000	51,506,000
Non-cash investing and financing activities:
Purchases of property and equipment through accounts payable and accruals	34,000	6,000	19,000
Operating lease right-of-use assets exchanged for lease obligations	585,000	658,000	1,228,000
Supplemental cash flow information:
Net cash paid for income taxes	$ 26,000	$ 858,000	$ 345,000