NEW YORK ( TheStreet) -- Heavily shorted LED market sapphire substrate provider Rubicon Technology ( RBCN) easily beat earnings expectations after Wednesday's closing bell, sending the shares higher in after-hours action. Bensenville, Ill.-based Rubicon reported fourth-quarter earnings of $15.4 million, or 64 cents a share, well ahead of the average estimate of analysts polled by Thomson Reuters for a profit of 50 cents a share in the December period. The company's fiscal first-quarter outlook was also strong as it forecast earnings of 62 to 65 cents a share for the three months ending in March vs. the current average analysts' view of 52 cents a share. Revenue of $29.5 million for the fourth quarter was ahead of Wall Street's consensus view of $26.8 million, as was the company's projection for revenue of $34 million to $36 million in the first quarter vs. the average analysts' estimate of $31 million. Rubicon shares were last quoted at $24.85, up 17.7%, on after-hours volume of around 330,000, according to Nasdaq.com. Over the past year, short interest in Rubicon Technology shares has doubled to more than 10 million shares of the 22.9 million outstanding shares of the LED company (even higher if the float is taken into account). Fears of a sapphire market glut have dogged the company. The most recent Nasdaq short interest report as of Jan. 31 shows that the 10 million share short position in Rubicon Technology remained steady headed into earnings season. Shorts had predicted that pricing would fall off, and there was a bearish call on Rubicon recently from Canaccord Adams for a fourth-quarter pricing peak. Beyond the printed earnings number and guidance, the Rubicon results showed better-than-expected success with its 6-inch sapphire wafer, a premium product that generates higher margins. It's an important differentiating factor for a company that has attracted heavy short interest based on the theory that margins will fall. Rubicon margins hits 63% in the fourth quarter. The company guided margins lower for the first quarter, but at guidance of high 50s for the first quarter, the margins are still healthy.