Exhibit 99.1

RUBICON TECHNOLOGY, INC. REPORTS FIRST QUARTER

2015 RESULTS OF OPERATIONS

Bensenville, Ill. – May 7, 2015— Rubicon Technology, Inc. (NASDAQ:RBCN), a leading provider of sapphire substrates and products to the LED, semiconductor, and optical industries, today reported financial results for its first quarter ended March 31, 2015.

The Company reported first quarter revenue of $8.9 million which was consistent with the prior quarter revenue and reduced its loss per share despite continued weakness in the LED market. Demand for the Company’s two-inch sapphire cores, primarily used in the mobile device market, increased in the period but was offset in part by lower revenue from four-inch LED core sales. The Company continued qualifying its large diameter PSS wafers and believes that PSS revenue will ramp in the second half of the year. A table with the breakdown of revenue is included with this press release.

Loss per share in the first quarter was $0.32 as compared with prior quarter loss of $0.36.

The Company also reviewed the status on key objectives for 2015, which include aggressively pursuing the potential of its PSS product, targeting high margin optical applications and driving down product costs. William Weissman, Rubicon’s CEO, commented, “The sapphire market continues to be very challenging but the actions we are taking during this difficult time in the market will position the Company to drive better margins from a more diverse set of products once the market improves.”

Second Quarter 2015 Guidance

The Company expects second quarter revenue and loss per share to be similar to the first quarter. While core sale volumes will likely be higher, total revenue is expected to be similar to the first quarter due to additional pricing pressure, particularly on two-inch

material. Loss per share is also expected to be similar to the first quarter with cost reductions offsetting the additional price pressure. Commenting on the Company’s outlook, Mr. Weissman said, “While we expect second quarter results to be comparable to the first quarter, we have visibility into growing PSS volumes in the second half of the year. With increased wafer revenue in combination with reducing product costs, we expect a meaningful improvement in operating results by the end of the year.”

Conference Call Details

Rubicon will host a conference call at 5:00 p.m. Eastern time on May 7, 2015 to review the first quarter 2015 results and the second quarter outlook. The conference call will be available to the public through a live audio web broadcast via the Internet. Log on through the Investor Relations section of Rubicon’s website at http://ir.rubicontechnology.com. An audio replay of the call will be available approximately two hours after the conclusion of the call. The audio replay will remain available until 9:00 a.m. Eastern time on May 14, 2015, and can be accessed by dialing (877) 344-7529 or (412) 317-0088 (international). Callers should reference conference ID 10064451. The webcast will be archived on the Company’s website.

About Rubicon Technology, Inc.

Rubicon Technology, Inc. is a vertically integrated advanced electronic materials provider specializing in monocrystalline sapphire for applications in light-emitting diodes (LEDs), optical systems and specialty electronic devices. Rubicon has a proprietary technology platform and expertise extending from the preparation of raw aluminum oxide through sapphire crystal growth and fabrication to large-diameter polished sapphire wafers and patterned sapphire substrates (PSS), enabling Rubicon to supply custom sapphire products with superior quality and precision. Rubicon is ISO 9001 certified and ITAR registered.

Further information is available at http://www.rubicontechnology.com.

Forward-Looking Statements

Certain of the statements in this release, particularly those preceded by, followed by or including the words “believes,” “expects,” “anticipates,” “intends,” “should,” “estimates,” or similar expressions, or those relating to or anticipating financial results for periods beyond the end of the first quarter of 2015, constitute “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. For those statements, the Company claims the protection of the safe harbor for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995. These forward-looking statements are based on our current expectations, estimates and projections about our industry, management’s beliefs and certain assumptions made by us. These statements are subject to risks and uncertainties that could cause actual results to differ materially from those expressed in, or implied by, the statements. These risks and uncertainties include changes in the average selling prices of sapphire products, our successful development and market acceptance of new products, dependence on key customers, potential disruptions in our supply of electricity, changes in our product mix, our ability to protect our intellectual property rights, the competitive environment, the availability and cost of raw materials, the cost of compliance with environmental standards, the ability to make effective acquisitions and successfully integrate newly acquired businesses into existing operations and other risks and uncertainties described in the Company’s most recent Form 10-K and other filings with the Securities and Exchange Commission. For these reasons, readers are cautioned not to place undue reliance on the Company’s forward-looking statements. Any forward-looking statement that the Company makes speaks only as of the date of such statement, and the Company undertakes no obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise. Comparisons of results for current and any prior periods are not intended to express any future trends or indications of future performance, unless expressed as such, and should only be viewed as historical data.

CONTACT:

Dee Johnson

Vice President, Investor Relations

847-457-3426

Rubicon Technology, Inc.

Condensed Consolidated Balance Sheets

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Rubicon Technology, Inc.

Condensed Consolidated Statements of Operations (unaudited)

(in thousands except share and per share amounts)

Rubicon Technology, Inc.

Condensed Consolidated Statements of Cash Flows (unaudited)

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Rubicon Technology, Inc.

Revenue by Product Group

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