Stock-based Compensation Expense (Tables)

6 Months Ended

Jun. 30, 2023

Stock-based Compensation Expense [Abstract]

Weighted-Average Assumptions for Stock Options

Employee Stock Options:

	Six Months Ended June 30,
	2023			2022
Risk-free interest rate		3.6	%		1.8	%
Dividend yield		0.0	%		0.0	%
Volatility		47.3	%		55.1	%
Expected life	6.3 years			6.3 years

Weighted-Average Assumptions for ESPP

ESPP:

	Six Months Ended June 30,
	2023			2022
Risk-free interest rate		5.2	%		0.6	%
Dividend yield		0.0	%		0.0	%
Volatility		36.7	%		50.2	%
Expected life	6 months			6 months

Stock-Based Compensation Expense

The following table summarizes stock-based compensation expense for the three and six months ended June 30, 2023 and 2022 (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2023		2022		2023		2022
Cost of sales	$	118	$	53	$	237	$	213
Research, development and patent expense		19,249		18,500		38,816		37,582
Selling, general and administrative expense		7,194		5,949		14,457		12,943
Total stock-based compensation expense	$	26,561	$	24,502	$	53,510	$	50,738