Note 3 - Stock-based Compensation

3 Months Ended

Jun. 30, 2023

Notes to Financial Statements

Share-Based Payment Arrangement [Text Block]

3. Stock-Based Compensation

The Company accounts for its stock-based compensation at fair value. The following table summarizes stock-based compensation expense by financial statement line item for the three months ended  June 30, 2023 and 2022 (in thousands):

	Three Months Ended June 30,
	2023		2022
Cost of revenues	$	109	$	29
Research and development		156		179
Selling, general and administrative		1,092		825
Total	$	1,357	$	1,033

The Company issued 672,500 shares of restricted stock and 53,675 shares of immediately vested common stock during the three months ended June 30, 2023. The Company issued 25,806 shares of immediately vested common stock during the three months ended June 30, 2022. These restricted stock awards generally vest over 2-3 years.  Awards for restricted stock include both time-based and performance-based awards.  For options and restricted stock awards that vest upon the passage of time, expense is being recorded over the vesting period.  Performance-based awards are expensed over the requisite service period based on probability of achievement.

The estimated fair value of the Company’s stock-based awards, less expected annual forfeitures, is amortized over the awards’ service period. The total unrecognized compensation cost for unvested stock options was less than $0.1 million at June 30, 2023.  This expense will be recognized over a weighted average of approximately 0.9 years. The total unrecognized compensation cost for unvested outstanding restricted stock was $7.7 million at June 30, 2023. This expense will be recognized over a weighted-average expense period of approximately 2.2 years.

The Company granted no stock options during the three months ended  June 30, 2023. The Company granted 20,564 stock options during the three months ended June 30, 2022.  The stock options granted during the three months ended June 30, 2022, will vest over 2 years. The weighted average assumptions used in the Black Scholes valuation model for stock options granted during the three months ended June 30, 2022 are as follows:

Expected volatility		71.40	%
Risk-free interest rate		3.10	%
Expected life (years)		6.14
Dividend yield	None