8. STOCK- BASED COMPENSATION (Tables)

3 Months Ended

Jun. 30, 2018

STOCK- BASED COMPENSATION

Summary of stock option activities

			Weighted
		Number of Shares	Average	Weighted
	Shares	Underlying	Remaining	Average
	Available for	Options	Contractual	Exercise		Intrinsic
	Grant	Outstanding	Life (Years)	Price		Value
Balance at March 31, 2018	4,444,301	7,874,267		$	5.45
Granted	(78,590)	78,590		$	7.70
Exercised	—	(300,528)		$	3.92	$	1,054,096
Forfeited	8,750	(38,550)		$	4.57
Balance at June 30, 2018	4,374,461	7,613,779	5.53	$	5.53
Options vested and exercisable		5,046,534	4.08	$	5.34	$	11,189,643
Options vested and expected to vest		7,556,754	5.51	$	5.53	$	15,312,078

Schedule of options outstanding by exercise price

				Number of	Options Outstanding			Options Exercisable
				Shares	Weighted		Weighted Average		Weighted
				Underlying	Average		Remaining	Number	Average
				Options	Exercise		Contractual	Vested and	Exercise
Exercise Price				Outstanding	Price		Life (Years)	Exercisable	Price
$	2.43	-	3.60	794,891	$	3.36	3.99	608,537	$	3.33
$	3.75	-	4.34	828,326	$	4.09	2.67	792,876	$	4.08
$	4.43	-	4.98	1,052,821	$	4.88	5.37	629,617	$	4.83
$	4.99	-	5.23	1,157,976	$	5.10	7.21	637,576	$	5.18
$	5.28	-	5.76	762,790	$	5.55	5.98	619,466	$	5.61
$	6.00	-	6.45	777,918	$	6.19	5.00	550,685	$	6.20
$	6.54	-	6.86	1,114,076	$	6.74	5.21	874,185	$	6.70
$	7.00	-	7.40	812,001	$	7.22	7.67	225,012	$	7.09
$	7.70	-	8.09	204,400	$	7.95	9.68	-	$	-
$	9.20			108,580	$	9.20	2.59	108,580	$	9.20
				7,613,779	$	5.53	5.53	5,046,534	$	5.34

Summary of stock-based compensation expense by line item

	Three Months Ended June 30,
	2018		2017
	(In thousands)
Cost of revenues	$	53	$	47
Research and development		323		267
Selling, general and administrative		166		164
Total	$	542	$	478

Schedule of weighted average assumptions

	Three Months Ended June 30,
	2018			2017
	(In thousands)
Stock Option Plans:
Risk-free interest rate		2.78	%		1.91	%
Expected life (in years)		5.00			5.00
Volatility		35.6	%		36.5	%
Dividend yield		—	%		—	%
Employee Stock Purchase Plan:
Risk-free interest rate		2.09	%		1.04	%
Expected life (in years)		0.50			0.50
Volatility		37.7	%		51.1	%
Dividend yield		—	%		—	%